METHOD FOR PRODUCING PEPTIDE COMPOUND

Abstract

A method for producing a peptide by conducting steps (1) condensing an N-protected amino acid or an N-protected peptide to an N-terminus of a C-protected amino acid or a C-protected peptide represented by formula (II):

##STR00001##

wherein Y represents an amino acid or a peptide with an unprotected N-terminus; R.sup.1, R.sup.2 and R.sup.3 each independently represent an optionally substituted aliphatic hydrocarbon group, an optionally substituted aromatic hydrocarbon group, or OR.sup.4 (wherein R.sup.4 represents an optionally substituted aliphatic or aromatic hydrocarbon group; two of R.sup.1, R.sup.2 and R.sup.3 may form a 5- to 7-membered ring together with the Si atom to which they are bonded; and the R.sup.1R.sup.2R.sup.3Si group has 8 or more carbon atoms and is bonded to a C-terminus of an amino acid or a peptide in Y, and (2) removing the protective group at the N-terminus of the peptide obtained in step (1).

Claims

1. A method for producing an amino acid or a peptide which comprises a step of removing a protective group at an N-terminus of an amino acid or a peptide represented by the formula (I):
P-AA-OSiR.sup.1R.sup.2R.sup.3 (I) wherein, AA represents a group derived from an amino acid or a peptide, P represents a protective group at the N-terminus, R.sup.1R.sup.2R.sup.3Si represents a protective group at the C-terminus, R.sup.1, R.sup.2 and R.sup.3 each independently represent an aliphatic hydrocarbon group which may have a substituent(s), an aromatic hydrocarbon group which may have a substituent(s) or OR.sup.4, where R.sup.4 represents an aliphatic hydrocarbon group which may have a substituent(s) or an aromatic hydrocarbon group which may have a substituent(s), two of R.sup.1, R.sup.2 and R.sup.3 may form a 5- to 7-membered ring together with the Si atom to which they are bonded, and a total number of the carbon atoms in the R.sup.1R.sup.2R.sup.3Si group is 8 or more.

2. A method for producing a peptide which comprises the following steps (1) and (2): (1) a step of condensing an N-protected amino acid or an N-protected peptide to an N-terminus of a C-protected amino acid or a C-protected peptide represented by the formula (II): ##STR00095## wherein, Y represents an amino acid an N-terminus of which is unprotected or a peptide an N-terminus of which is unprotected, R.sup.1, R.sup.2 and R.sup.3 each independently represent an aliphatic hydrocarbon group which may have a substituent(s), an aromatic hydrocarbon group which may have a substituent(s) or OR.sup.4, where R.sup.4 represents an aliphatic hydrocarbon group which may have a substituent(s) or an aromatic hydrocarbon group which may have a substituent(s), two of R.sup.1, R.sup.2 and R.sup.3 may form a 5- to 7-membered ring together with the Si atom to which they are bonded, a total number of the carbon atoms in the R.sup.1R.sup.2R.sup.3Si group is 8 or more, and the R.sup.1R.sup.2R.sup.3Si group is bonded to a C-terminus of an amino acid or a peptide in Y; and (2) a step of removing the protective group at the N-terminus of the peptide obtained in the step (1).

3. The method for producing a peptide according to claim 2, which comprises the following steps (1) and (2): (1) a step of condensing an N-protected amino acid or an N-protected peptide to an N-terminus of a C-protected amino acid or a C-protected peptide represented by the formula (II): ##STR00096## wherein, Y represents an amino acid an N-terminus of which is unprotected or a peptide an N-terminus of which is unprotected, R.sup.1, R.sup.2 and R.sup.3 each independently represent an aliphatic hydrocarbon group which may have a substituent(s), a total number of the carbon atoms in the R.sup.1R.sup.2R.sup.3Si group is 8 or more, and the R.sup.1R.sup.2R.sup.3Si group is bonded to a C-terminus of an amino acid or a peptide in Y; (2) a step of removing the protective group at the N-terminus of the peptide obtained in the step (1).

4. A method for producing a peptide which comprises the following steps (1) to (3): (1) a step of condensing an N-protected amino acid or an N-protected peptide to an N-terminus of a C-protected amino acid or a C-protected peptide represented by the formula (II): ##STR00097## wherein, Y represents an amino acid an N-terminus of which is unprotected or a peptide an N-terminus of which is unprotected, R.sup.1, R.sup.2 and R.sup.3 each independently represent an aliphatic hydrocarbon group which may have a substituent(s), an aromatic hydrocarbon group which may have a substituent(s) or OR.sup.4, where R.sup.4 represents an aliphatic hydrocarbon group which may have a substituent(s) or an aromatic hydrocarbon group which may have a substituent(s), two of R.sup.1, R.sup.2 and R.sup.3 may form a 5- to 7-membered ring together with the Si atom to which they are bonded, a total number of the carbon atoms in the R.sup.1R.sup.2R.sup.3Si group is 8 or more, and the R.sup.1R.sup.2R.sup.3Si group is bonded to a C-terminus of an amino acid or a peptide in Y; (2) a step of removing the protective group at the N-terminus of the peptide obtained in the step (1); (3) a step of condensing an N-protected amino acid or an N-protected peptide to the N-terminus of the peptide obtained in the step (2).

5. The method for producing a peptide according to claim 4, which comprises the following steps (1) to (3): (1) a step of condensing an N-protected amino acid or an N-protected peptide to an N-terminus of a C-protected amino acid or a C-protected peptide represented by the formula (II): ##STR00098## wherein, Y represents an amino acid an N-terminus of which is unprotected or a peptide an N-terminus of which is unprotected, R.sup.1, R.sup.2 and R.sup.3 each independently represent an aliphatic hydrocarbon group which may have a substituent(s), a total number of the carbon atoms in the R.sup.1R.sup.2R.sup.3Si group is 8 or more, and the R.sup.1R.sup.2R.sup.3Si group is bonded to a C-terminus of an amino acid or a peptide in Y; (2) a step of removing the protective group at the N-terminus of the peptide obtained in the step (1); (3) a step of condensing an N-protected amino acid or an N-protected peptide to the N-terminus of the peptide obtained in the step (2).

6. The method for producing a peptide according to claim 4, which comprises a step of removing the protective group at the C-terminus of the peptide obtained in the step (3).

7. The method for producing a peptide according to claim 4, which further comprises one or more repeating of the following steps (4) and (5): (4) a step of removing the protective group at the N-terminus of the peptide obtained in the step (3) or the step (5). (5) a step of condensing an N-protected amino acid or an N-protected peptide to an N-terminus of the peptide obtained in the step (4).

8. The method for producing a peptide according to claim 7, which comprises a step of removing the protective group at the C-terminus of the peptide obtained in the step (5).

9. The producing method according to claim 1, wherein a total number of the carbon atoms in the R.sup.1R.sup.2R.sup.3Si group is 10 to 100.

10. The producing method according to claim 1, wherein a total number of the carbon atoms in the R.sup.1R.sup.2R.sup.3Si group is 10 to 40.

11. The producing method according to claim 1, wherein among R.sup.1, R.sup.2 and R.sup.3, two or three of them each independently represent a secondary or tertiary aliphatic hydrocarbon group.

12. The producing method according to claim 11, wherein among R.sup.1, R.sup.2 and R.sup.3, two of them each independently represent a secondary aliphatic hydrocarbon group, and the remaining one represents a secondary or tertiary aliphatic hydrocarbon group which may have a substituent(s) and a group different from the above two.

13. The producing method according to claim 11, wherein among R.sup.1, R.sup.2 and R.sup.3, two of them each independently represent a tertiary aliphatic hydrocarbon group.

14. The producing method according to claim 1, wherein among R.sup.1, R.sup.2 and R.sup.3, two or three of them each independently represent a secondary or tertiary C.sub.3-6 alkyl group or a C.sub.3-6 cycloalkyl group.

15. The producing method according to claim 14, wherein among R.sup.1, R.sup.2 and R.sup.3, two of them each independently represent a secondary C.sub.3-6 alkyl group or a C.sub.3-6 cycloalkyl group, and the remaining one represents a secondary or tertiary C.sub.3-6 alkyl group or a C.sub.3-6 cycloalkyl group, which may have a substituent(s), and is different from the above two.

16. The producing method according to claim 14, wherein among R.sup.1, R.sup.2 and R.sup.3, two of them each independently represent a tertiary C.sub.4-6 alkyl group.

17. The producing method according to claim 1, wherein among R.sup.1, R.sup.2 and R.sup.3, two or three of them each independently represent a t-butyl group, an i-propyl group, an s-butyl group, a cyclopentyl group or a cyclohexyl group.

18. The producing method according to claim 17, wherein among R.sup.1, R.sup.2 and R.sup.3, one of them represents a t-butyl group or a cumyl group, and the remaining two are each independently represent a t-butyl group, an i-propyl group, an s-butyl group, a cyclopentyl group or a cyclohexyl group.

19. The producing method according to claim 17, wherein among R.sup.1, R.sup.2 and R.sup.3, two of them are t-butyl groups, and the remaining one is an i-butyl group, a benzyl group, an octadecyl group or a (trimethylsilyl)methyl group.

20. The producing method according to claim 1, wherein the R.sup.1R.sup.2R.sup.3Si group is a di-s-butyl-t-butylsilyl group, a di-t-butylisobutylsilyl group, a di-t-butyloctadecylsilyl group, a benzyl-di-t-butylsilyl group, a tri-t-butylsilyl group, a di-i-propyl-t-butylsilyl group, a di-i-propylcumylsilyl group, a di-cyclopentylcumylsilyl group, a di-cyclohexylcumylsilyl group, a di-s-butylcumylsilyl group or a di-t-butyl {(trimethyl silyl)methyl}silyl group.

21. The producing method according to claim 1, wherein the R.sup.1R.sup.2R.sup.3Si group is a di-t-butylphenethoxysilyl group or a di-t-butylphenylsilyl group.

22. The producing method according to claim 1, wherein R.sup.1, R.sup.2 and R.sup.3 are OR.sup.4, where R.sup.4 represents a tertiary aliphatic hydrocarbon group.

23. The producing method according to claim 1, wherein the R.sup.1R.sup.2R.sup.3Si group is a tri-t-butoxysilyl group.

24. The producing method according to claim 1, wherein the amino acid or the peptide is constituted by an -amino acid.

25. The producing method according to claim 1, wherein the protective group at the N-terminus of the N-protected amino acid or the N-protected peptide is a carbamate protective group.

26. The producing method according to claim 1, wherein the protective group at the N-terminus of the N-protected amino acid or the N-protected peptide is a benzyloxycarbonyl group, a 9-fluorenylmethoxycarbonyl group or a t-butoxycarbonyl group.

27. Use of a group represented by the following formula (III): ##STR00099## wherein, R.sup.1, R.sup.2 and R.sup.3 each independently represent an aliphatic hydrocarbon group which may have a substituent(s), an aromatic hydrocarbon group which may have a substituent(s) or OR.sup.4, where R.sup.4 represents an aliphatic hydrocarbon group which may have a substituent(s) or an aromatic hydrocarbon group which may have a substituent(s), two of R.sup.1, R.sup.2 and R.sup.3 may form a 5- to 7-membered ring together with the Si atom to which they are bonded, a total number of the carbon atoms in the R.sup.1R.sup.2R.sup.3Si group is 8 or more, and a wavy line is a bonding position to a residue at the C-terminus of the amino acid or the peptide, as a protective group of a C-terminus of an amino acid or a peptide in an N-terminal elongation reaction of a peptide.

Description

EXAMPLES

[0152] In the following, the present invention is further explained in detail by referring to Reference Synthetic Examples and Synthetic Examples, but the present invention is not limited to these Examples.

[0153] In the present specification, when an amino acid, etc., are indicated by abbreviations, each indication is based on an abbreviation by IUPAC-IUB Commission on Biochemical Nomenclature or an abbreviation commonly used in this field of the art.

[0154] The proton nuclear magnetic resonance (.sup.1H-NMR) of Examples is measured by using JNM-ECP300 manufactured by JEOL Ltd., or JNM-ECX300 manufactured by JEOL Ltd., or Ascend500 manufactured by Bruker in deuterated chloroform or deuterated dimethylsulfoxide solvent otherwise specifically mentioned, and the chemical shift is shown by a 6 value (ppm) when tetramethylsilane is used as an internal standard (0.0 ppm).

[0155] In the description of the NMR spectrum, s means singlet, d means doublet, t means triplet, q means quartet, dd means doublet of doublet, dt means doublet of triplet, m means multiplet, br means broad, J means a coupling constant, Hz means hertz, CDCl.sub.3 means deuterated chloroform and DMSO-d6 means deuterated dimethylsulfoxide.

[0156] The high-performance liquid chromatography/mass analysis is measured by using any of ACQUITY UPLC H-Class/QDa manufactured by Waters Corporation, ACQUITY UPLC H-Class/SQD2 manufactured by Waters Corporation, or LC-20AD/Triple Tof5600 manufactured by Shimadzu Corporation otherwise specifically mentioned.

[0157] In the description of the high-performance liquid chromatography/mass analysis, ESI+ is a positive mode of an electrospray ionization method, and M+H means a proton adduct and M+Na means a sodium adduct.

[0158] In the description of the high-performance liquid chromatography/mass analysis, ESI means a negative mode of an electrospray ionization method, and MH means a proton defected material.

[0159] Purification by silica gel column chromatography is carried out by using either of Hi-Flash column manufactured by Yamazen Corporation, SNAP Ultra Silica Cartridge manufactured by Biotage, silica gel 60 manufactured by Merck or PSQ60B manufactured by Fuji Silysia Chemical Ltd., otherwise specifically mentioned.

Synthetic Example 1: Synthesis of H-MePhe-OBIBS

[0160] ##STR00010##

[0161] (i) Cbz-MePhe-OH (2.50 g, 7.98 mmol) and di-t-butylisobutylsilane triflate (3.08 g, 8.83 mmol) were mixed with methylene chloride (30.0 g), the mixture was cooled to 0 C., and after adding N,N-diisopropylethylamine (1.24 g, 9.58 mmol) dropwise, stirred at room temperature for 2 hours. The obtained reaction mixture was washed with an aqueous saturated ammonium chloride solution (20.3 g), the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-MePhe-OBIBS (3.45 g, Yield: 85%) as a colorless liquid. MASS (ESI+) m/z; 512.38 (M+H)+

[0162] (ii) Cbz-MePhe-OBIBS (0.60 g, 1.17 mmol) was mixed with 2,2,2-trifluoroethanol (6.0 g), and after adding 10% by mass PdC (60.2 mg, 0.057 mmol) thereto, the mixture was stirred under hydrogen gas atmosphere at room temperature for 2 hours. The reaction mixture was filtered and the obtained filtrate was concentrated. The concentrate was dissolved in methylene chloride (30.3 g), and water (20.0 g) was added thereto and the liquids were separated. The organic layer was concentrated to obtain H-MePhe-OBIBS (0.42 g, Yield: 97%).

[0163] MASS (ESI+) m/z; 378.35 (M+H)+

Synthetic Example 2: Synthesis of Fmoc-MePhe-MePhe-MePhe-OBIBS

[0164] ##STR00011##

[0165] (i) H-MePhe-OBIBS (0.41 g, 1.08 mmol) was dissolved in methylene chloride (8.9 g), Cbz-MePhe-OH (0.56 g, 1.77 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.34 g, 1.76 mmol) were added thereto under ice-cooling and stirred for 3 hours. After returned to room temperature and stirring for 2 hours, chloroform (30.9 g) and water (20.2 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (20.0 g), 5% by mass aqueous citric acid solution (20.1 g) and an aqueous saturated ammonium chloride solution (20.0 g) in this order, the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-MePhe-MePhe-OBIBS (0.65 g, Yield: 89%) as a colorless liquid.

[0166] MASS (ESI+) m/z; 673.51 (M+H)+

[0167] (ii) Cbz-MePhe-MePhe-OBIBS (0.41 g, 0.61 mmol) was dissolved in 2,2,2-trifluoroethanol (4.0 g), and after adding 10% by mass PdC (41.2 mg, 0.039 mmol), the mixture was stirred under hydrogen gas atmosphere at room temperature for 22 hours. The reaction mixture was filtered and the obtained filtrate was concentrated. The concentrate was dissolved in chloroform (30.0 g), and water (20.0 g) was added thereto and the liquids were separated. The organic layer was concentrated to obtain H-MePhe-MePhe-OBIBS (0.32 g, Yield: 99%).

[0168] MASS (ESI+) m/z; 539.46 (M+H)+

[0169] (iii) H-MePhe-MePhe-OBIBS (0.30 g, 0.56 mmol) and Fmoc-MePhe-OH (0.34 g, 0.84 mmol) were dissolved in methylene chloride (6.1 g), and under ice-cooling, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.16 g, 0.84 mmol) was added thereto and the mixture was stirred for 6 hours. After diluting the obtained reaction mixture with chloroform (30.0 g), it was washed with an aqueous saturated ammonium chloride solution (20.2 g) and an aqueous saturated sodium hydrogen carbonate solution (20.1 g) in this order. The obtained organic layer was dried over magnesium sulfate, and then, the solution obtained by filtration was concentrated. The obtained residue was purified by silica gel column chromatography to obtain Fmoc-MePhe-MePhe-MePhe-OBIBS (0.49 g, Yield: 95%) as a white solid.

[0170] MASS (ESI+) m/z; 922.51 (M+H)+

Synthetic Example 3: Synthesis of Boc-MePhe-MePhe-MePhe-MePhe-OBIBS

[0171] ##STR00012##

[0172] (i) Fmoc-MePhe-MePhe-MePhe-OBIBS (0.30 g, 0.32 mmol) was mixed with methylene chloride (6.0 g) and cooled to 0 C., and after adding diethylamine (0.60 g, 8.2 mmol), the mixture was stirred for 1 hour. After returning to room temperature and stirring for 22 hours, the mixture was diluted with chloroform (30.1 g), washed with an aqueous saturated ammonium chloride solution (20.2 g) twice, and the organic layer was concentrated, and then, purified by silica gel column chromatography to obtain H-MePhe-MePhe-MePhe-OBIBS (0.21 g, Yield: 93%) as a yellow liquid. MASS (ESI+) m/z; 700.44 (M+H)+

[0173] (ii) H-MePhe-MePhe-MePhe-OBIBS (0.20 g, 0.28 mmol) and Boc-MePhe-OH (0.12 g, 0.43 mmol) were mixed with methylene chloride (4.0 g), the mixture was cooled to 0 C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.083 g, 0.43 mmol) was added thereto and the mixture was stirred for 3 hours. After returning to room temperature and stirring for 3 hours, the obtained reaction mixture was diluted with chloroform (30.0 g), and washed with an aqueous saturated sodium hydrogen carbonate solution (20.2 g) and an aqueous saturated ammonium chloride solution (20.0 g) in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-MePhe-MePhe-MePhe-MePhe-OBIBS (0.25 g, Yield: 90%) as a white solid.

[0174] MASS (ESI+) m/z; 961.58 (M+H)+

Synthetic Example 4: Synthesis of Cbz-MePhe-MePhe-MePhe-MePhe-MePhe-OBIBS

[0175] ##STR00013##

[0176] (i) Boc-MePhe-MePhe-MePhe-MePhe-OBIBS (0.18 g, 0.19 mmol) was mixed with methylene chloride (4.0 g), the mixture was cooled to 0 C., 15% by mass hydrogen chloride-1,4-dioxane (2.0 g, 8.2 mmol) was added thereto, and then, the mixture was stirred for 3 hours. After returning to room temperature and stirring for 4 hours, the obtained reaction mixture was diluted with chloroform (60.0 g), and then, an aqueous saturated sodium hydrogen carbonate solution (40.3 g) was added thereto and the liquids were separated, and the organic layer was washed with water (40.1 g). The obtained organic layer was concentrated to obtain H-MePhe-MePhe-MePhe-MePhe-OBIBS (0.16 g, Yield: 99%) as a white solid.

[0177] MASS (ESI+) m/z; 861.53 (M+H)+

[0178] (ii) H-MePhe-MePhe-MePhe-MePhe-OBIBS (0.16 g, 0.18 mmol) and Cbz-MePhe-OH (0.038 g, 0.29 mmol) were mixed with methylene chloride (3.2 g), the mixture was cooled to 0 C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.054 g, 0.28 mmol) was added thereto and the mixture was stirred for 7 hours. The obtained reaction mixture was diluted with chloroform (40.2 g), and then, washed with an aqueous saturated sodium hydrogen carbonate solution (30.0 g) and an aqueous saturated ammonium chloride solution (30.0 g) in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-MePhe-MePhe-MePhe-MePhe-MePhe-OBIBS (0.19 g, Yield: 93%) as a white solid.

[0179] MASS (ESI+) m/z; 1156.65 (M+H)+

Synthetic Example 5: Synthesis of Cbz-MePhe-MePhe-MePhe-MePhe-MePhe-OH

[0180] ##STR00014##

[0181] Cbz-MePhe-MePhe-MePhe-MePhe-MePhe-OBIBS (0.15 g, 0.13 mmol) was mixed with methylene chloride (3.0 g), the mixture was cooled to 0 C., 1M fluorinated tetrabutylammonium-tetrahydrofuran solution (0.14 mL, 0.14 mmol) was added thereto and the mixture was stirred for 2 hours. To the obtained reaction mixture were added 1M hydrochloric acid (20 g) and chloroform (40.0 g) and the liquids were separated, and the organic layer was washed with 1% by mass aqueous sodium chloride solution. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-MePhe-MePhe-MePhe-MePhe-MePhe-OH (0.12 g, Yield: 95%) as a white solid.

[0182] MASS (ESI+) m/z; 958.47 (M+H)+

Synthetic Example 6: Synthesis of H-MePhe-OBIBS

[0183] ##STR00015##

[0184] (i) Boc-MePhe-OH (0.88 g, 3.17 mmol) and N,N-diisopropylethylamine (0.46 g, 3.59 mmol) were mixed with methylene chloride (13.3 g), the mixture was cooled to 0 C., di-t-butylisobutylsilane triflate (1.00 g, 2.87 mmol) was added dropwise thereto and the mixture was stirred for 3 hours. The obtained reaction mixture was washed with 5% by mass aqueous sodium hydrogen carbonate solution (10.0 g) and an aqueous saturated ammonium chloride solution (10.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-MePhe-OBIBS (1.32 g, Yield: 95.9%) as a colorless liquid.

[0185] MASS (ESI+) m/z; 478.46 (M+H)+

[0186] (ii) Boc-MePhe-OBIBS (0.10 g, 0.21 mmol) was mixed with methylene chloride (2.7 g), the mixture was cooled to 0 C., 15% by mass hydrogen chloride-1,4-dioxane (0.82 g, 3.2 mmol) was added thereto, and the mixture was stirred at 5 C. for 25 hours. Water was added to the obtained reaction mixture (6.0 g) and the liquids were separated, and the organic layer was washed with 8% by mass aqueous sodium hydrogen carbonate solution (2.0 g). The obtained organic layer was concentrated to obtain H-MePhe-OBIBS (0.078 g, Yield: 99%) as a white solid.

Synthetic Example 7: Synthesis of Boc-Ala-MePhe-MePhe-OBIBS

[0187] ##STR00016##

[0188] (i) Boc-MePhe-OH (0.50 g, 1.79 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (0.35 g, 1.83 mmol) were mixed with methylene chloride (8.9 g), the mixture was cooled to 0 C., a methylene chloride solution (3.1 g) of H-MePhe-OBIBS (0.42 g, 1.12 mmol) was added thereto and after the mixture was stirred at 0 C. for 3.5 hours, Boc-MePhe-OH (0.17 g, 0.60 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.12 g, 0.61 mmol) were added thereto and the mixture was stirred for 18 hours. To the obtained reaction mixture was added 2M hydrochloric acid (2.3 mL, 4.6 mmol) and the liquids were separated. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-MePhe-MePhe-OBIBS (0.73 g, Yield: 102%) as a colorless liquid.

[0189] MASS (ESI+) m/z; 639.56 (M+H)+

[0190] (ii) Boc-MePhe-MePhe-OBIBS (0.32 g, 0.50 mmol) was mixed with methylene chloride, the mixture was cooled to 0 C., 15% by mass hydrogen chloride-1,4-dioxane (3.3 g, 12.8 mmol) was added thereto and the mixture was stirred at 5 C. for 20 hours. Water was added to the obtained reaction mixture (6.0 g) and the liquids were separated, and the organic layer was washed with 8% by mass aqueous sodium hydrogen carbonate solution (4.0 g) and water (10.0 g) in this order. The obtained organic layer was concentrated to obtain H-MePhe-MePhe-OBIBS (0.25 g, Yield: 92%) as a colorless liquid.

[0191] MASS (ESI+) m/z; 539.45 (M+H)+

[0192] (iii) Boc-Ala-OH (0.16 g, 0.87 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (0.17 g, 0.88 mmol) were mixed with methylene chloride (3.7 g), the mixture was cooled to 0 C., a methylene chloride solution (3.2 g) of H-MePhe-MePhe-OBIBS (0.21 g, 0.40 mmol) was added thereto, and then, the mixture was stirred at 0 C. for 3 hours. To the obtained reaction mixture was added 1M hydrochloric acid (2.3 mL, 2.3 mmol) and the liquids were separated, and the organic layer was washed with 8% by mass aqueous sodium hydrogen carbonate solution (2.3 g). The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Ala-MePhe-MePhe-OBIBS (0.24 g, Yield: 85%) as a white solid.

[0193] MASS (ESI+) m/z; 710.57 (M+H)+

Synthetic Example 8: Synthesis of Boc-Ala-MePhe-MePhe-OH

[0194] ##STR00017##

[0195] Boc-Ala-MePhe-MePhe-OBIBS (0.093 g, 0.13 mmol) was mixed with methanol (0.40 g) and tetrahydrofuran (1.3 g), the mixture was cooled to 0 C., potassium fluoride (0.015 g, 0.26 mmol) was added thereto, and then, the mixture was stirred for 18 hours. To the obtained reaction mixture were added an aqueous saturated sodium chloride solution (1.0 g), water (4.0 g) and methylene chloride (5.4 g), the liquids were separated, and methylene chloride (5.4 g) was added to the aqueous layer to carry out extraction. The organic layers were combined and washed with 0.25M hydrochloric acid (8.0 mL). The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Ala-MePhe-MePhe-OH (0.064 g, Yield: 96%) as a colorless liquid.

[0196] MASS (ESI+) m/z; 534.31 (M+Na)+

Synthetic Example 9: Synthesis of H-Arg(Ts)-OBIBS

[0197] ##STR00018##

[0198] (i) Boc-Arg(Ts)-OH (0.80 g, 1.87 mmol) and N,N-diisopropylethylamine (0.29 g, 2.24 mmol) were mixed with methylene chloride (16.0 g), the mixture was cooled to 0 C., di-t-butylisobutylsilane triflate (0.72 g, 2.06 mmol) was added dropwise thereto, then, the mixture was stirred at room temperature for 2 hours, and N,N-diisopropylethylamine (0.12 g, 0.94 mmol) and di-t-butylisobutylsilane triflate (0.33 g, 0.94 mmol) were each added thereto and the mixture was stirred for 1 hour. To the obtained reaction mixture were added water (10.0 g), 10% by mass aqueous citric acid solution (6.0 g), water (6.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Arg(Ts)-OBIBS (0.98 g, Yield: 83%) as a colorless liquid.

[0199] .sup.1H-NMR (CDCl.sub.3)

[0200] ppm: 0.86 (2H, d, J=6.7 Hz), 0.95 (6H, d, J=6.4 Hz), 1.04 (9H, s), 1.04 (9H, s), 1.41 (9H, s), 1.55-1.72 (3H, m), 1.80-2.09 (2H, m), 2.39 (3H, s), 3.05-3.50 (2H, br), 4.15-4.30 (1H, m), 5.32 (1H, d, J=8.3 Hz), 6.15-6.95 (2H, br), 7.21 (2H, d, J=8.0 Hz), 7.74 (2H, d, J=8.0 Hz)

[0201] MASS (ESI+) m/z; 627.5 (M+H)+

[0202] (ii) Boc-Arg(Ts)-OBIBS (0.63 g, 1.00 mmol) was mixed with methylene chloride (12.6 g), the mixture was cooled to 0 C., 15% by mass hydrogen chloride-1,4-dioxane (1.22 g, 5.00 mmol) was added thereto, then, the mixture was stirred at 0 C. for 12.5 hours, and 15% by mass hydrogen chloride-1,4-dioxane (1.22 g, 5.00 mmol) was added thereto, and the mixture was stirred for 4 hours. To the obtained reaction mixture was added 5% by mass aqueous sodium hydrogen carbonate solution (10.1 g) and the liquids were separated, and the organic layer was further washed with water (8.0 g) twice. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain H-Arg(Ts)-OBIBS (0.50 g, Yield: 95%) as a white solid.

[0203] .sup.1H-NMR (CDCl.sub.3)

[0204] ppm: 0.87 (2H, d, J=6.9 Hz), 0.94 (3H, d, J=6.6 Hz), 0.95 (3H, d, J=6.6 Hz), 1.04 (9H, s), 1.04 (9H, s), 1.41 (9H, s), 1.55-2.09 (5H, m), 2.38 (3H, s), 3.12-3.25 (2H, br), 3.43 (1H, dd, J=8.71, 4.51 Hz), 6.28-6.75 (2H, br), 7.22 (2H, d, J=8.1 Hz), 7.76 (2H, d, J=8.1 Hz)

[0205] MASS (ESI+) m/z; 527.4 (M+H)+

Synthetic Example 10: Synthesis of Boc-Arg(Ts)-Ala-Arg(Ts)-OBIBS

[0206] ##STR00019##

[0207] (i) H-Arg(Ts)-OBIBS (0.49 g, 0.93 mmol) and Boc-Ala-OH (0.35 g, 1.86 mmol) were mixed with methylene chloride (19.6 g), the mixture was cooled to 0 C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.36 g, 1.86 mmol) was added thereto, and then, the mixture was stirred at 0 C. for 1.5 hours. Water was added to the obtained reaction mixture (10.0 g) and the liquids were separated, and a minute amount of N,N-dimethyl-4-aminopyridine and 5% by mass aqueous sodium hydrogen carbonate solution (5.0 g) were added thereto and the liquids were separated. The obtained organic layer was further washed with water (10.0 g), the organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Ala-Arg(Ts)-OBIBS (0.64 g, Yield: 99%) as a white solid.

[0208] .sup.1H-NMR (CDCl.sub.3)

[0209] ppm: 0.86 (2H, d, J=6.6 Hz), 0.94 (3H, d, J=6.6 Hz), 0.94 (3H, d, J=6.6 Hz), 1.04 (9H, s), 1.04 (9H, s), 1.34 (3H, d, J=7.2 Hz), 1.41 (9H, s), 1.55-1.72 (3H, m), 1.90-2.09 (2H, m), 2.39 (3H, s), 3.05-3.50 (2H, br), 4.05-4.20 (1H, m), 4.45-4.55 (1H, m), 5.12 (1H, br), 6.20-6.55 (3H, br), 6.91 (1H, d, J=8.4 Hz), 7.21 (2H, d, J=8.4 Hz), 7.75 (2H, d, J=8.4 Hz)

[0210] MASS (ESI+) m/z; 698.6 (M+H)+

[0211] (ii) Boc-Ala-Arg(Ts)-OBIBS (0.63 g, 0.90 mmol) was mixed with methylene chloride (12.6 g), the mixture was cooled to 0 C., 15% by mass hydrogen chloride-1,4-dioxane solution (1.10 g, 4.50 mmol) was added thereto, then, the mixture was stirred at 5 C. for 16.5 hours, 5% by mass aqueous sodium hydrogen carbonate solution (9.1 g) was added thereto and the liquids were separated, and the organic layer was further washed with 10% by mass brine solution twice. The obtained organic layer was dried over magnesium sulfate and filtered, and the obtained solution was concentrated to obtain H-Ala-Arg(Ts)-OBIBS (0.50 g, Yield: 93%) as a white solid.

[0212] .sup.1H-NMR (CDCl.sub.3)

[0213] ppm: 0.88 (2H, d, J=6.9 Hz), 0.94 (3H, d, J=6.6 Hz), 0.95 (3H, d, J=6.6 Hz), 1.04 (9H, s), 1.05 (9H, s), 1.34 (3H, d, J=7.2 Hz), 1.50-1.80 (3H, m), 1.90-2.09 (2H, m), 2.38 (3H, s), 3.00-3.60 (2H, br), 3.54 (1H, dd, J=6.6, 13.8 Hz), 4.46-4.52 (1H, m), 5.12 (1H, br), 6.35-6.90 (3H, br), 7.21 (2H, d, J=8.4 Hz), 7.75 (2H, d, J=8.4 Hz), 8.11 (1H, br)

[0214] MASS (ESI+) m/z; 598.4 (M+H)+

[0215] (iii) H-Ala-Arg(Ts)-OBIBS (0.47 g, 0.79 mmol) and Boc-Arg(Ts)-OH (0.51 g, 1.19 mmol) were mixed with methylene chloride (18.8 g), the mixture was cooled to 0 C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.23 g, 1.19 mmol) was added thereto, and then, the mixture was stirred at 0 C. for 2 hours. Water was added to the obtained reaction mixture (10.0 g) and the liquids were separated, a minute amount of N,N-dimethyl-4-aminopyridine, 5% by mass aqueous sodium hydrogen carbonate solution, 10% by mass brine solution and 5% by mass aqueous citric acid solution were added thereto and the liquids were separated. The obtained organic layer was further washed with water and brine solution, and after concentrating the organic layer, the concentrate was purified by silica gel column chromatography to obtain Boc-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.72 g, Yield: 91%) as a white solid.

[0216] .sup.1H-NMR (CDCl.sub.3)

[0217] ppm: 0.85 (2H, d, J=6.6 Hz), 0.93 (6H, d, J=6.6 Hz), 1.02 (18H, s), 1.42 (12H, s), 1.55-1.75 (7H, m), 1.85-2.09 (2H, m), 2.39 (6H, s), 2.80-3.90 (4H, br), 4.20-4.55 (3H, br), 5.85-7.00 (6H, br), 7.21 (2H, d, J=8.1 Hz), 7.45-7.80 (5H, br)

[0218] MASS (ESI+) m/z; 1008.6 (M+H)+

Synthetic Example 11: Synthesis of Boc-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS

[0219] ##STR00020##

[0220] (i) Boc-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.69 g, 0.68 mmol) was mixed with methylene chloride (13.7 g), the mixture was cooled to 5 C., 15% by mass hydrogen chloride-1,4-dioxane solution (0.83 g, 3.4 mmol) was added thereto, and then, the mixture was stirred at 5 C. for 19 hours, 5% by mass aqueous sodium hydrogen carbonate solution was added thereto and the liquids were separated, to the obtained organic layer was further added 10% by mass brine solution, 5% by mass aqueous sodium hydrogen carbonate solution and an aqueous ammonia and the liquids were separated, and the organic layer was washed with 10% by mass brine solution. After the obtained organic layer was dried over magnesium sulfate, and the solution obtained by filtration was concentrated to obtain H-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.58 g, Yield: 94%) as a white solid.

[0221] .sup.1H-NMR (CDCl.sub.3)

[0222] ppm: 0.84 (2H, d, J=6.6 Hz), 0.92 (6H, d, J=6.6 Hz), 1.02 (18H, s), 1.39 (12H, s), 1.45-1.68 (16H, m), 2.36 (9H, s), 3.0-3.60 (7H, br), 4.00-4.90 (3H, br), 6.00-7.10 (9H, br), 7.18 (7H, d, J=7.8 Hz), 7.68 (8H, m)

[0223] MASS (ESI+) m/z; 908.6 (M+H)+

[0224] (ii) H-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.57 g, 0.63 mmol) and Boc-Arg(Ts)-OH (0.40 g, 0.95 mmol) were mixed with methylene chloride (22.8 g), the mixture was cooled to 1 C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.18 g, 0.95 mmol) was added thereto and the mixture was stirred at 0 C. for 1.5 hours. Water was added to the obtained reaction mixture and the liquids were separated, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.64 g, Yield: 78%) as a white solid.

[0225] .sup.1H-NMR (CDCl.sub.3)

[0226] ppm: 0.85 (2H, d, J=6.6 Hz), 0.93 (6H, d, J=6.6 Hz), 1.02 (18H, s), 1.42 (12H, s), 1.55-1.75 (7H, m), 1.85-2.09 (2H, m), 2.39 (6H, s), 2.80-3.90 (4H, br), 4.20-4.55 (3H, br), 5.85-7.00 (6H, br), 7.21 (2H, d, J=8.1 Hz), 7.45-7.80 (5H, br)

[0227] MASS (ESI+) m/z; 1318.6 (M+H)+

Synthetic Example 12: Synthesis of Boc-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS

[0228] ##STR00021##

[0229] (i) Boc-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.63 g, 0.48 mmol) was mixed with methylene chloride (12.6 g), the mixture was cooled to 0 C., 15% by mass hydrogen chloride-1,4-dioxane solution (0.58 g, 2.4 mmol) was added thereto, and then, the mixture was stirred at 5 C. for 19.5 hours, and after adding 15% by mass hydrogen chloride-1,4-dioxane solution (0.31 g, 1.3 mmol) thereto, the mixture was further stirred for 3 hours. 5% by mass aqueous sodium hydrogen carbonate solution was added to the mixture, the liquids were separated and the obtained solution was concentrated to obtain H-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.60 g, Yield: 104%) as a white solid.

[0230] .sup.1H-NMR (CDCl.sub.3)

[0231] ppm: 0.84 (2H, d, J=6.6 Hz), 0.91 (6H, d, J=6.6 Hz), 1.01 (18H, s), 1.31 (3H, d, J=6.6 Hz), 1.75-2.10 (17H, m), 2.36 (9H, s), 3.00-3.60 (7H, br), 4.00-4.85 (3H, br), 6.00-7.10 (9H, br), 7.19 (7H, d, J=7.2 Hz), 7.4-8.4 (8H, br)

[0232] MASS (ESI+) m/z; 1218.6 (M+H)+

[0233] (ii) H-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.58 g, 0.48 mmol), Boc-Arg(Ts)-OH (0.31 g, 0.72 mmol) was mixed with methylene chloride (23.3 g), the mixture was cooled to 0 C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.14 g, 0.72 mmol) was added thereto and the mixture was stirred at 0 C. for 1 hour. Water was added to the obtained reaction mixture, the liquids were separated, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.67 g, Yield: 86%) as a white solid.

[0234] .sup.1H-NMR (CDCl.sub.3)

[0235] ppm: 0.84 (2H, d, J=6.0 Hz), 0.91 (6H, d, J=5.8 Hz), 1.00 (18H, s), 1.38 (12H, br), 1.45-2.09 (16H, br), 2.36 (12H, s), 2.80-3.40 (8H, br), 3.90-4.85 (4H, br), 5.65-7.10 (12H, br), 7.19 (8H, d, J=7.2 Hz), 7.4-8.1 (11H, br)

[0236] MASS (ESI+) m/z; 1628.7 (M+H)+

Synthetic Example 13: Synthesis of Boc-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS

[0237] ##STR00022##

[0238] (i) Boc-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.66 g, 0.41 mmol) was mixed with methylene chloride (13.2 g), the mixture was cooled to 5 C., 15% by mass hydrogen chloride-1,4-dioxane solution (0.79 g, 3.3 mmol) was added thereto and the mixture was stirred at 5 C. for 17.5 hours. 5% by mass aqueous sodium hydrogen carbonate solution, the liquids were separated and the obtained solution was concentrated to obtain H-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.59 g, Yield: 95%) as a white solid.

[0239] .sup.1H-NMR (CDCl.sub.3)

[0240] ppm: 0.84 (2H, d, J=6.6 Hz), 0.90 (6H, d, J=6.6 Hz), 0.99 (18H, s), 1.29 (3H, br), 1.7-2.1 (18H, m), 2.33 (9H, s), 2.7-3.6 (9H, br), 3.9-4.9 (4H, br), 5.9-6.9 (11H, br), 6.9-7.2 (10H, br), 7.4-8.5 (12H, br)

[0241] MASS (ESI+) m/z; 1528.7 (M+1)+

[0242] (ii) H-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.57 g, 0.37 mmol) and Boc-Arg(Ts)-OH (0.11 g, 0.56 mmol) were mixed with methylene chloride (22.8 g), the mixture was cooled to 0 C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.11 g, 0.56 mmol) was added thereto and the mixture was stirred at 0 C. for 1 hour. Water was added to the obtained reaction mixture and the liquids were separated, the organic layer was washed with a saturated brine solution, then, concentrated and purified by silica gel column chromatography to obtain Boc-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.645 g, Yield: 102%) as a white solid.

[0243] .sup.1H-NMR (CDCl.sub.3)

[0244] ppm: 0.83 (2H, d, J=6.3 Hz), 0.91 (6H, d, J=6.0 Hz), 1.00 (18H, s), 1.3-1.5 (15H, br), 1.6-2.1 (17H, br), 2.36 (12H, s), 2.7-3.90 (8H, br), 4.2-4.8 (6H, br), 5.8-7.1 (11H, br), 7.18 (9H, d, J=6.9 Hz), 7.4-8.1 (12H, br)

[0245] MASS (ESI+) m/z; 1699.7 (M+H)+

Synthetic Example 14: Synthesis of Fmoc-Cys(Trt)-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS

[0246] ##STR00023##

[0247] (i) Boc-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.63 g, 0.37 mmol) was mixed with methylene chloride (12.6 g), the mixture was cooled to 6 C., 15% by mass hydrogen chloride-1,4-dioxane solution (0.72 g, 3.0 mmol) was added thereto and the mixture was stirred at 6 C. for 15 hours. 5% by mass aqueous sodium hydrogen carbonate solution was added to the mixture and the liquids were separated, and the organic layer was washed with a saturated brine solution and the obtained solution was concentrated to obtain H-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.58 g, Yield: 98%) as a white solid.

[0248] .sup.1H-NMR (CDCl.sub.3)

[0249] ppm: 0.83 (2H, d, J=6.6 Hz), 0.90 (6H, d, J=6.3 Hz), 0.99 (18H, s), 1.27 (6H, br), 1.7-2.1 (20H, m), 2.34 (12H, s), 2.7-3.6 (10H, br), 3.9-4.9 (4H, br), 5.9-6.9 (12H, br), 6.9-7.2 (10H, br), 7.4-8.5 (13H, br)

[0250] MASS (ESI+) m/z; 1599.7 (M+H)+

[0251] (ii) H-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.57 g, 0.36 mmol) and Fmoc-Cys(Trt)-OH (0.31 g, 0.54 mmol) were mixed with methylene chloride (22.8 g), the mixture was cooled to 0 C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.10 g, 0.54 mmol) was added thereto and the mixture was stirred at 0 C. for 2 hours. Water was added to the obtained reaction mixture and the liquids were separated, the organic layer was concentrated, solvent substitution to ethyl acetate was carried out twice and precipitated solid was collected by filtration and dried to obtain Fmoc-Cys(Trt)-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.71 g, Yield: 92%) as a white solid.

[0252] .sup.1H-NMR (DMSO-d6)

[0253] ppm: 0.81 (2H, d, J=6.9 Hz), 0.90 (611, d, J=6.6 Hz), 0.99 (18H, s), 1.16 (6H, m), 1.3-1.8 (16H, br), 1.95 (11, m), 2.31 (12H, br), 2.41 (2H, m), 2.9-3.2 (8H, br), 4.1-4.4 (10H, m), 6.4-7.1 (911, br), 7.27 (30H, m), 7.6-7.8 (12H, m), 7.8-8.1 (6H, br), 8.24 (1H, br)

[0254] MASS (ESI+) m/z; 2166.9 (M+H)+

Synthetic Example 15: Synthesis of Ac-Cys(Trt)-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS

[0255] ##STR00024##

[0256] (i) Fmoc-Cys(Trt)-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.59 g, 0.27 mmol) was mixed with methylene chloride (11.7 g) at room temperature, and after adding diethylamine (0.99 g, 13.5 mmol) thereto, the mixture was stirred for 16.5 hours. 20% by mass aqueous ammonium chloride solution was added to the mixture and the liquids were separated twice, the organic layer was washed with 5% by mass aqueous sodium hydrogen carbonate solution and a saturated brine solution, and the organic layer was dried over magnesium sulfate, solvent substitution to ethyl acetate was carried out twice and the obtained solid was collected by filtration and dried to obtain H-Cys(Trt)-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.43 g, Yield: 81%) as a white solid.

[0257] .sup.1H-NMR (DMSO-d6)

[0258] ppm: 0.81 (2H, d, J=6.3 Hz), 0.90 (6H, d, J=6.6 Hz), 0.99 (18H, s), 1.16 (6H, m), 1.3-1.8 (17H, br), 1.93 (1H, m), 2.31 (14H, br), 2.9-3.2 (9H, br), 4.1-4.4 (6H, m), 6.4-7.1 (9H, br), 7.27 (27H, m), 7.61 (9H, m), 7.8-8.1 (5H, br), 8.21 (1H, br),

[0259] MASS (ESI+) m/z; 1944.8 (M+H)+

[0260] (ii) H-Cys(Trt)-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.37 g, 0.19 mmol) and N,N-dimethyl-4-aminopyridine (0.14 g, 1.14 mmol) were mixed with methylene chloride (14.8 g), the mixture was cooled to 0 C., acetic anhydride (0.14 g, 0.54 mmol) was added thereto and the mixture was stirred at 0 C. for 2.5 hours. Water was added to the obtained reaction mixture, the liquids were separated, and the organic layer was washed with a saturated brine solution and concentrated, solvent substitution to ethyl acetate was carried out twice and the precipitated solid was collected by filtration and dried to obtain Ac-Cys(Trt)-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.38 g, Yield: 100%) as a white solid.

[0261] .sup.1H-NMR (DMSO-d6)

[0262] ppm: 0.81 (2H, d, J=6.6 Hz), 0.90 (6H, d, J=6.3 Hz), 0.99 (18H, s), 1.16 (6H, m), 1.3-1.8 (17H, br), 1.84 (3H, s), 1.95 (1H, m), 2.32 (14H, m), 2.9-3.2 (8H, br), 4.1-4.4 (7H, m), 6.4-7.1 (9H, br), 7.27 (28H, m), 7.62 (8H, m), 7.8-8.1 (5H, br), 8.1-8.3 (1H, br)

[0263] MASS (ESI+) m/z; 1986.8 (M+H)+

Synthetic Example 16: Synthesis of Ac-Cys(Trt)-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OH

[0264] ##STR00025##

[0265] Ac-Cys(Trt)-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OBIBS (0.36 g, 0.18 mmol) was mixed with methanol (7.2 g) at room temperature, cesium fluoride (0.14 g, 0.90 mmol) was added thereto and the mixture was stirred for 23 hours. Phosphoric acid was added thereto and the mixture was stirred for 1 hour, then, the solid was collected by filtration and dried, and the obtained solid was suspended and washed with water and then collected by filtration and dried to obtain Ac-Cys(Trt)-Ala-Arg(Ts)-Arg(Ts)-Arg(Ts)-Ala-Arg(Ts)-OH (0.27 g, Yield: 85%) as a white solid.

[0266] .sup.1H-NMR (DMSO-d6)

[0267] ppm: 1.15 (3H, d, J=7.2 Hz), 1.21 (3H, d, J=7.5 Hz), 1.3-1.8 (16H, br), 1.84 (3H, s), 2.32 (14H, m), 2.9-3.2 (8H, br), 3.69 (1H, m), 4.1-4.4 (6H, br), 6.4-7.1 (8H, br), 7.27 (26H, m), 7.62 (9H, m), 7.8-8.2 (6H, br), 8.2-8.3 (1H, br)

[0268] MASS (ESI+) m/z; 1788.7 (M+H)+

Synthetic Example 17: Synthesis of H-Phe-Phe-O(t-Bu)Silolane

[0269] ##STR00026##

[0270] (i) 1-(t-Butyl)silolane (0.75 g, 5.29 mmol) was dissolved in methylene chloride (20.9 g), trifluoromethanesulfonic acid (0.69 g, 4.6 mmol) was added thereto at 0 C., and the mixture was stirred at room temperature for 2 hours. The obtained reaction mixture was added to a methylene chloride (10.6 g) solution of Cbz-Phe-Phe-OH (1.57 g, 3.51 mmol) and imidazole (0.36 g, 5.27 mmol) at 0 C., and after returning to room temperature, the mixture was stirring for 1.5 hours. To the obtained reaction mixture were added an aqueous saturated ammonium chloride solution (8.0 g) and water (8.0 g), and the liquids were separated. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-O(t-Bu)Silolane (1.59 g, Yield: 77%) as a white solid.

[0271] MASS (ESI+) m/z; 587.36 (M+H)+

[0272] (ii) Cbz-Phe-Phe-O(t-Bu)Silolane (0.75 g, 1.71 mmol) was dissolved in 2,2,2-trifluoroethanol (10.4 g), 10% by mass PdC (80 mg, 0.08 mmol) was added thereto and the mixture was stirred under a hydrogen gas atmosphere for 1 hour. The reaction mixture was filtered and the obtained filtrate was concentrated to obtain H-Phe-Phe-O(t-Bu)Silolane(0.63 g, Yield: 100%) as a brown oil.

[0273] MASS (ESI+) m/z; 453.38 (M+H)+

Synthetic Example 18: Synthesis of Fmoc-Ser(Bn)-Ala-Phe-Phe-O(t-Bu)Silolane

[0274] ##STR00027##

[0275] (i) H-Phe-Phe-O(t-Bu)Silolane (0.58 g, 1.28 mmol) and Cbz-Ala-OH (0.44 g, 1.96 mmol) were dissolved in methylene chloride (7.7 g), 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide hydrochloride (0.35 g, 1.84 mmol) was added thereto under ice-cooling and the mixture was stirred for 1.5 hours. The obtained reaction mixture was washed with 4% by mass hydrochloric acid (5.8 g) and an aqueous saturated sodium hydrogen carbonate solution (5.8 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Ala-Phe-Phe-O(t-Bu)Silolane (0.535 g, Yield: 65%) as a white solid.

[0276] MASS (ESI+) m/z; 658.41 (M+H)+

[0277] (ii) Cbz-Ala-Phe-Phe-O(t-Bu)Silolane (0.50 g, 0.77 mmol) was dissolved in 2,2,2-trifluoroethanol (8.3 g), 10% by mass PdC (55 mg, 0.052 mmol) was added thereto and the mixture was stirred under a hydrogen gas atmosphere for 2.5 hours. After filtering the reaction mixture, the obtained filtrate was concentrated to obtain H-Ala-Phe-Phe-O(t-Bu)Silolane (0.440 g, Yield: 110%) as a brown solid.

[0278] MASS (ESI+) m/z; 524.42 (M+H)+

[0279] (iii) H-Ala-Phe-Phe-O(t-Bu)Silolane (0.401 g, 0.766 mmol) and Fmoc-Ser(Bn)-OH (0.484 g, 1.16 mmol) were dissolved in methylene chloride (5.3 g), and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.224 g, 1.17 mmol) was added thereto under ice-cooling and the mixture was stirred for 1 hour. The obtained reaction mixture was washed with 4% by mass hydrochloric acid (4.0 g) and an aqueous saturated sodium hydrogen carbonate solution (4.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Ser(Bn)-Ala-Phe-Phe-O(t-Bu)Silolane (0.213 g, Yield: 30%) as a colorless solid.

[0280] MASS (ESI+) m/z; 923.57 (M+H)+

Synthetic Example 19: Synthesis of H-Phe-Phe-OTIPS

[0281] ##STR00028##

[0282] (i) Cbz-Phe-Phe-OH (1.01 g, 2.26 mmol) and TIPS-Cl (0.55 g, 2.85 mmol) were mixed with methylene chloride (20.2 g), the mixture was cooled to 0 C., and imidazole (0.18 g, 2.64 mmol) was added thereto and the mixture was stirred for 2 hours. After returned to room temperature and stirring for 2 hours, chloroform and water were added to the obtained reaction mixture and the liquids were separated. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OTIPS (1.20 g, Yield: 88%) as a white solid.

[0283] MASS (ESI+) m/z; 603.32 (M+H)+

[0284] (ii) Cbz-Phe-Phe-OTIPS (0.50 g, 0.83 mmol) was mixed with 2,2,2-trifluoroethanol (5.0 g) and t-butyl methyl ether (10.0 g), 10% by mass PdC (0.30 g) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at room temperature for 5 hours. After filtering the reaction mixture, the obtained filtrate was concentrated to obtain H-Phe-Phe-OTIPS (0.40 g, Yield: 100%) as a colorless oil.

[0285] MASS (ESI+) m/z; 616.35 (M+H)+

Synthetic Example 20: Synthesis of Fmoc-Phe-Phe-Phe-Phe-OTIPS

[0286] ##STR00029##

[0287] (i) Cbz-Phe-OH (0.23 g, 0.77 mmol) was dissolved in methylene chloride (3.0 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.15 g, 0.78 mmol) was added thereto under ice-cooling and a methylene chloride (3.0 g) solution of H-Phe-Phe-OTIPS (0.27 g, 0.58 mmol) was added dropwise thereto and the mixture was stirred for 2 hours. The obtained reaction mixture was diluted with chloroform, washed with an aqueous saturated ammonium chloride solution and an aqueous saturated sodium hydrogen carbonate solution in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-Phe-OTIPS (0.30 g, Yield: 68%) as a white solid.

[0288] MASS (ESI+) m/z; 749.39 (M+H)+

[0289] (ii) Cbz-Phe-Phe-Phe-OTIPS (0.25 g, 0.33 mmol) was mixed with 2,2,2-trifluoroethanol (5.0 g) and t-butyl methyl ether (2.5 g), 10% by mass PdC (0.10 g) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at room temperature for 3 hours. After filtering the reaction mixture, the obtained filtrate was concentrated to obtain H-Phe-Phe-Phe-OTIPS (0.21 g, Yield: 100%) as a colorless oil.

[0290] MASS (ESI+) m/z; 469.29 (M+H)+

[0291] (iii) Fmoc-Phe-OH (0.15 g, 0.39 mmol) was dissolved in methylene chloride (2.0 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.08 g, 0.42 mmol) was added thereto under ice-cooling and a methylene chloride (2.5 g) solution of H-Phe-Phe-Phe-OTIPS (0.20 g, 0.32 mmol) was added dropwise thereto and the mixture was stirred for 3 hours. The obtained reaction mixture was diluted with chloroform, and washed with an aqueous saturated ammonium chloride solution and an aqueous saturated sodium hydrogen carbonate solution in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Phe-Phe-Phe-Phe-OTIPS (0.25 g, Yield: 77%) as a white solid.

[0292] MASS (ESI+) m/z; 985.49 (M+H)+

Synthetic Example 21: Synthesis of Cbz-Phe-Phe-OSi(tBu).SUB.2.(Me)

[0293] ##STR00030##

[0294] Di-t-butylmethylsilane (0.50 g, 3.16 mmol) was dissolved in methylene chloride (2.5 g), trifluorosulfonic acid (0.47 g, 3.16 mmol) was added thereto at 0 C. and the mixture was stirred at room temperature for 1 hour. The obtained reaction mixture was added to a methylene chloride (5.0 g) solution of Cbz-Phe-Phe-OH (1.55 g, 3.48 mmol) and N, N-diisopropylethylamine (0.49 g, 3.79 mmol) at 0 C., and then, the mixture was stirred for 1 hour. The obtained reaction mixture was diluted with t-butyl methyl ether, then, washed with 5% by mass potassium hydrogen carbonate twice and further washed with water. The obtained organic layer was washed with 5% by mass citric acid and further washed with water twice. The obtained organic layer was concentrated to obtain Cbz-Phe-Phe-OSi(tBu).sub.2(Me) (1.90 g, Yield: 100%) as a colorless oil.

[0295] MASS (ESI+) m/z; 603.4 (M+H)+

Synthetic Example 22: Synthesis of H-Phe-Phe-Phe-OSi(tBu).SUB.2.(Me)

[0296] ##STR00031##

[0297] (i) Cbz-Phe-Phe-OSi(tBu).sub.2(Me) (1.90 g, 3.16 mmol) was dissolved in methylene chloride (9.5 g) and 2,2,2-trifluoroethanol (19.0 g) at 40 C., 10% by mass PdC (170 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere for 2 hours. After filtering the reaction mixture, the obtained filtrate was concentrated. The obtained concentrate was dissolved in methylene chloride (15.0 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.91 g, 4.74 mmol) and Boc-Phe-OH (1.09 g, 4.11 mmol) were added thereto under ice-cooling and the mixture was stirred for 16 hours. The obtained reaction mixture was diluted with methyl cyclopentyl ether, then, washed with water, 10% by mass aqueous potassium hydrogen carbonate solution (5.0 g) and N,N-dimethyl-4-aminopyridine (0.02 g) were added thereto, and the liquids were separated. The obtained organic layer was washed with water twice, then, washed with 10% by mass aqueous citric acid solution, and further washed with water twice. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Phe-Phe-Phe-OSi(tBu).sub.2(Me) (2.08 g, Yield: 92%) as a colorless oil.

[0298] MASS (ESI+) m/z; 716.49 (M+H)+

[0299] (ii) Boc-Phe-Phe-Phe-OSi(tBu).sub.2(Me) (1.70 g, 2.37 mmol) was dissolved in methylene chloride (34.0 g), 15% by mass hydrogen chloride-1,4-dioxane (4.62 g, 19.0 mmol) was added thereto and the mixture was stirred for 17 hours. The obtained reaction mixture was washed with 10% by mass aqueous potassium hydrogen carbonate solution and further washed with water twice. The obtained organic layer was concentrated to obtain H-Phe-Phe-Phe-OSi(tBu).sub.2(Me) (1.24 g, Yield: 85%) as a colorless oil.

[0300] MASS (ESI+) m/z; 616.39 (M+H)+

Reference Synthetic Example 1: Synthesis of HSi(sBu).SUB.2.(tBu)

[0301] ##STR00032##

[0302] Heptane (6.8 g) and 1.0M s-butyl lithium-hexane solution (17.5 mL, 18 mmol) were mixed at 0 C., then, a heptane (6.8 g) solution of t-butyltrichlorosilane (1.00 g, 5.22 mmol) was added thereto and the mixture was stirred at 90 C. for 4 hours. The obtained reaction mixture was cooled to 0 C., 2-propanol (0.78 g), heptane (14 g) and water (20 g) were added thereto and the liquids were separated. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain HSi(sBu).sub.2(tBu) (0.46 g, Yield: 44%) as a colorless liquid.

[0303] .sup.1H-NMR (CDCl.sub.3)

[0304] ppm: 0.86-0.98 (12H, m), 1.01 (9H, s), 1.07-1.38 (6H, m)

Synthetic Example 23: Synthesis of H-Phe-OSi(sBu).SUB.2.(tBu)

[0305] ##STR00033##

[0306] (i) HSi(sBu).sub.2(tBu) (0.41 g, 2.06 mmol) was dissolved in methylene chloride (6.8 g), trifluoromethanesulfonic acid (0.31 g, 2.1 mmol) was added thereto at 0 C. and the mixture was stirred at room temperature for 2 hours. The obtained reaction mixture was added to a methylene chloride (3.3 g) solution of Cbz-Phe-OH (0.51 g, 1.72 mmol) and imidazole (0.18 g, 2.64 mmol) at 0 C., and then, the mixture was stirred at room temperature for 2 hours. To the obtained reaction mixture were added an aqueous saturated ammonium chloride solution (4.0 g) and water (1.0 g), and the liquids were separated. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-OSi(sBu).sub.2(tBu) (0.822 g, Yield: 97%) as a colorless liquid.

[0307] MASS (ESI+) m/z; 498.35 (M+H)+

[0308] (ii) Cbz-Phe-OSi(sBu).sub.2(tBu) (0.60 g, 1.20 mmol) was dissolved in 2,2,2-trifluoroethanol (8.3 g), 10% by mass PdC (59.3 mg, 0.06 mmol) was added thereto and the mixture was stirred under a hydrogen gas atmosphere for 5 hours. After filtering the reaction mixture, the obtained filtrate was concentrated. The obtained concentrate was purified by silica gel column chromatography to obtain H-Phe-OSi(sBu).sub.2(tBu) (0.382 g, Yield: 88%) as a colorless liquid.

[0309] MASS (ESI+) m/z; 364.45 (M+H)+

Synthetic Example 24: Synthesis of Fmoc-Ser(Bn)-Phe-Phe-OSi(sBu).SUB.2.(tBu)

[0310] ##STR00034##

[0311] (i) Cbz-Phe-OH (0.47 g, 1.56 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.29 g, 1.53 mmol) were dissolved in methylene chloride (2.7 g), H-Phe-OSi(sBu).sub.2(tBu) (0.33 g, 0.92 mmol) was added thereto under ice-cooling and the mixture was stirred for 40 minutes. The obtained reaction mixture was washed with 4% by mass hydrochloric acid (3.0 g) and an aqueous saturated sodium hydrogen carbonate solution (3.0 g) in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-Si(sBu).sub.2(tBu) (0.589 g, Yield: 100%) as a colorless oil.

[0312] MASS (ESI+) m/z; 645.47 (M+H)+

[0313] (ii) Cbz-Phe-Phe-OSi(sBu).sub.2(tBu) (0.58 g, 0.89 mmol) was dissolved in 2,2,2-trifluoroethanol (8.1 g), 10% by mass PdC (54.5 mg, 0.05 mmol) was added thereto and the mixture was stirred under a hydrogen gas atmosphere for 3 hours. The reaction mixture was filtered and the obtained filtrate was concentrated to obtain H-Phe-Phe-OSi(sBu).sub.2(tBu) (0.48 g, Yield: 100%) as a colorless oil.

[0314] MASS (ESI+) m/z; 511.43 (M+H)+

[0315] (iii) H-Phe-Phe-OSi(sBu).sub.2(tBu) (0.46 g, 0.89 mmol) and Fmoc-Ser(Bn)-OH (0.56 g, 1.34 mmol) were dissolved in methylene chloride (6.0 g), 1-ethyl-3-(3-dimethyl-aminopropyl)carbodiimide hydrochloride (0.26 g, 1.37 mmol) was added thereto under ice-cooling and the mixture was stirred for 1 hour. The obtained reaction mixture was washed with 4% by mass hydrochloric acid (5.0 g) and an aqueous saturated sodium hydrogen carbonate solution (5.0 g) in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Ser(Bn)-Phe-Phe-OSi(sBu).sub.2(tBu) (0.76 g, Yield: 93%) as a pale yellow solid.

[0316] MASS (ESI+) m/z; 910.59 (M+H)+

Synthetic Example 25: Synthesis of Boc-Ala-Ser(Bn)-Phe-Phe-OSi(sBu).SUB.2.(tBu)

[0317] ##STR00035##

[0318] (i) Fmoc-Ser(Bn)-Phe-Phe-OSi(sBu).sub.2(tBu) (0.567 g, 0.623 mmol) was mixed with methylene chloride (7.6 g), diethylamine (0.92 g, 12.5 mmol) was added thereto at 0 C., and the mixture was stirred at 5 C. for 18 hours. To the obtained reaction mixture was added 4% by mass hydrochloric acid (6.0 g) and the liquids were separated. After concentrating the organic layer, the concentrate was purified by silica gel chromatography to obtain H-Ser(Bn)-Phe-Phe-OSi(sBu).sub.2(tBu) (0.348 g, Yield: 81%) as a colorless oil.

[0319] MASS (ESI+) m/z; 688.52 (M+H)+

[0320] (ii) H-Ser(Bn)-Phe-Phe-OSi(sBu).sub.2(tBu) (0.320 g, 0.465 mmol) and Boc-Ala-OH (0.132 g, 0.697 mmol) were dissolved in methylene chloride (4.3 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.141 g, 0.738 mmol) was added thereto under ice-cooling and the mixture was stirred for 1 hour. To the mixed solution were added Boc-Ala-OH (0.019 g, 0.10 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.017 g, 0.088 mmol) and the mixture was stirred for 40 minutes. The obtained reaction mixture was washed with 4% by mass hydrochloric acid (3.0 g) and an aqueous saturated sodium hydrogen carbonate solution (3.0 g) in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Ala-Ser(Bn)-Phe-Phe-OSi(sBu).sub.2(tBu) (0.356 g, Yield: 89%) as a white solid.

[0321] MASS (ESI+) m/z; 859.54 (M+H)+

Synthetic Example 26: Synthesis of Fmoc-Pro-Ala-Ser(Bn)-Phe-Phe-OH

[0322] ##STR00036##

[0323] (i) Boc-Ala-Ser(Bn)-Phe-Phe-OSi(sBu).sub.2(tBu) (0.322 g, 0.375 mmol) was dissolved in methylene chloride (4.3 g), the mixture was cooled to 0 C., 15% by mass hydrogen chloride-1,4-dioxane (2.7 g, 10.4 mmol) was added thereto and the mixture was stirred at the same temperature for 20 hours. The obtained reaction mixture was washed with 5% by mass aqueous sodium chloride solution (4.0 g), 8% by mass aqueous sodium chloride solution (5.0 g), an aqueous saturated sodium hydrogen carbonate solution (3.0 g) and water (5.0 g) in this order. The obtained organic layer was concentrated to obtain H-Ala-Ser(Bn)-Phe-Phe-OSi(sBu).sub.2(tBu) (0.225 g, Yield: 79%) as a white solid.

[0324] MASS (ESI+) m/z; 759.58 (M+H)+

[0325] (ii) H-Ala-Ser(Bn)-Phe-Phe-OSi(sBu).sub.2(tBu) (0.22 g, 0.29 mmol) and Fmoc-Pro-OH (0.20 g, 0.59 mmol) were dissolved in methylene chloride (2.9 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.12 g, 0.60 mmol) was added thereto under ice-cooling and the mixture was stirred for 1 hour. The obtained reaction mixture was washed with 4% by mass hydrochloric acid (2.0 g) and an aqueous saturated sodium hydrogen carbonate solution (2.0 g) in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Pro-Ala-Ser(Bn)-Phe-Phe-OSi(sBu).sub.2(tBu) (0.32 g, Yield: 100%) as a white solid.

[0326] MASS (ESI+) m/z; 1078.59 (M+H)+

[0327] (iii) Fmoc-Pro-Ala-Ser(Bn)-Phe-Phe-OSi(sBu).sub.2(tBu) (0.13 g, 0.12 mmol) was mixed with methanol (0.55 g) and tetrahydrofuran (1.8 g), potassium fluoride (0.01 g, 0.25 mmol) was added thereto at 0 C. and the mixture was stirred for 3 hours. To the obtained reaction mixture were added 7% by mass aqueous sodium chloride solution (3.0 g), and methylene chloride (2.7 g) was added thereto and the liquids were separated. Methylene chloride (3.0 g) was added to the obtained aqueous layer to carry out extraction twice, and the organic layers were mixed. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Pro-Ala-Ser(Bn)-Phe-Phe-OH (0.08 g, Yield: 72%) as a white solid.

[0328] MASS (ESI+) m/z; 880.49 (M+H)+

Reference Synthetic Example 2: Synthesis of Cbz-Phe-OSi(tBu).SUB.2.(Bn)

[0329] ##STR00037##

[0330] (i) Di-t-butylchlorosilane (0.10 g, 0.58 mmol) was mixed with tetrahydrofuran (0.9 g), the mixture was cooled to 0 C., 2.0M benzyl magnesium chloride-tetrahydrofuran solution (0.34 mL, 0.68 mmol) was added thereto, and the mixture was stirred at room temperature for 3 hours. This solution was cooled to 0 C., benzyl magnesium chloride-tetrahydrofuran solution (0.17 mL, 0.34 mmol) was added thereto and the mixture was stirred at room temperature for 30 minutes. To the obtained reaction mixture were added 10% by mass aqueous ammonium chloride solution (3.0 g) and toluene (4.0 g) and the liquids were separated. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain di-t-butylbenzylsilane (0.11 g, Yield: 83%) as a colorless liquid.

[0331] .sup.1H-NMR (CDCl.sub.3)

[0332] ppm: 0.99 (18H, s), 2.22 (2H, d, J=3.5 Hz), 3.56 (1H, t, J=3.5 Hz), 7.03-7.28 (5H, m) (ii) Di-t-butylbenzylsilane (0.07 g, 0.31 mmol) was dissolved in methylene chloride (1.1 g), trifluoromethanesulfonic acid (0.05 g, 0.32 mmol) was added thereto at 0 C. and the mixture was stirred at room temperature for 1 hour. The obtained reaction mixture was added to a methylene chloride (0.5 g) solution of Cbz-Phe-OH (0.08 g, 0.27 mmol) and imidazole (0.03 g, 0.41 mmol) at 0 C., and after returning to room temperature, the mixture was stirred for 5 hours. The liquids of the obtained reaction mixture were separated using an aqueous saturated ammonium chloride solution (1.0 g) and water (1.0 g). The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-OSi(tBu).sub.2(Bn) (0.09 g, Yield: 66%) as a colorless liquid.

[0333] MASS (ESI+) m/z; 532.11 (M+H)+

Synthetic Example 27: Synthesis of Cbz-Phe-Phe-OSi(tBu).SUB.2.(Bn)

[0334] ##STR00038##

[0335] Cbz-Phe-OSi(tBu).sub.2(Bn) (0.15 g, 0.28 mmol) was dissolved in 2,2,2-trifluoroethanol (3.0 g) at 40 C., 10% by mass PdC (15 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere for 2 hours. 10% by mass PdC (20 mg) was further added to the mixture, then, the mixture was stirred under a hydrogen gas atmosphere for 4 hours. The reaction mixture was filtered and the obtained filtrate was concentrated. The obtained concentrate was dissolved in methylene chloride (1.1 g), then, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.11 g, 0.56 mmol) and Cbz-Phe-OH (0.17 g, 0.56 mmol) were added thereto under ice-cooling and the mixture was stirred for about 2 hours. The obtained reaction mixture was diluted with methylene chloride, and then, washed with 5% by mass hydrochloric acid, and further washed with water three times. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OSi(tBu).sub.2(Bn) (0.18 g, Yield: 96%) as a colorless oil.

[0336] MASS (ESI+) m/z; 679.48 (M+H)+

Synthetic Example 28: Synthesis of Boc-Ala-Phe-Phe-OSi(tBu).SUB.2.(Bn)

[0337] ##STR00039##

[0338] Cbz-Phe-Phe-OSi(tBu).sub.2(Bn) (0.17 g, 0.25 mmol) was dissolved in methylene chloride (3.4 g) and 2,2,2-trifluoroethanol (0.34 g) at 40 C., 10% by mass PdC (17 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere for 2 hours. The reaction mixture was filtered and the obtained filtrate was concentrated. The obtained concentrate was dissolved in methylene chloride (1.4 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.10 g, 0.50 mmol) and Cbz-Phe-OH (0.10 g, 0.50 mmol) were added thereto under ice-cooling and the mixture was stirred for 4 hours. The obtained reaction mixture was diluted with methylene chloride and then washed with water three times. The obtained organic layer was concentrated and the residue was purified by silica gel column chromatography to obtain Boc-Ala-Phe-Phe-OSi(tBu).sub.2(Bn) (0.18 g, Yield: 100%) as a colorless oil.

[0339] MASS (ESI+) m/z; 716.14 (M+H)+

Synthetic Example 29: Synthesis of Fmoc-Cys(Trt)-Ala-Phe-Phe-OSi(tBu).SUB.2.(Bn)

[0340] ##STR00040##

[0341] Boc-Ala-Phe-Phe-OSi(tBu).sub.2(Bn) (0.18 g, 0.25 mmol) was dissolved in methylene chloride (5.4 g) at room temperature, 15% by mass hydrogen chloride-1,4-dioxane (0.49 g, 2.0 mmol) was added thereto and the mixture was stirred for 25 hours. The obtained reaction mixture was diluted with methylene chloride, then, washed with 10% by mass aqueous potassium hydrogen carbonate solution, and further washed with water twice. The obtained organic layer was concentrated and dissolved in methylene chloride (1.54 g), under ice-cooling, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.096 g, 0.50 mmol) and Fmoc-Cys(Trt)-OH (0.29 g, 0.50 mmol) were added thereto under ice-cooling and stirred for 3 hours. The obtained reaction mixture was concentrated and purified by silica gel column chromatography to obtain Fmoc-Cys(Trt)-Ala-Phe-Phe-OSi(tBu).sub.2(Bn) (0.27 g, Yield: 90%) as a white solid.

[0342] MASS (ESI+) m/z; 1183.54 (M+H)+

Synthetic Example 30: Synthesis of Cbz-MeAla-Cys(Trt)-Ala-Phe-Phe-OSi(tBu).SUB.2.(Bn)

[0343] ##STR00041##

[0344] Fmoc-Cys(Trt)-Ala-Phe-Phe-OSi(tBu).sub.2(Bn) (0.15 g, 0.13 mmol) was dissolved in methylene chloride (4.5 g) at room temperature, diethylamine (0.46 g, 6.5 mmol) was added thereto and the mixture was stirred for 7 hours. The obtained reaction mixture was diluted with methylene chloride, and washed with 5% by mass aqueous sodium carbonate solution and further washed with water twice. The obtained organic layer was concentrated, and then, purified by silica gel column chromatography to obtain a white solid. The obtained solid was dissolved in methylene chloride (1.22 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.05 g, 0.26 mmol) and Fmoc-Cys(Trt)-OH (0.06 g, 0.26 mmol) were added thereto under ice-cooling, and the mixture was stirred for 2 hours. The obtained reaction mixture was concentrated, and then, purified by silica gel column chromatography to obtain Cbz-MeAla-Cys(Trt)-Ala-Phe-Phe-OSi(tBu).sub.2(Bn) (0.11 g, Yield: 75%) as a white solid.

[0345] MASS (ESI+) m/z; 1180.94 (M+H)+

Synthetic Example 31: Synthesis of Cbz-MeAla-Cys(Trt)-Ala-Phe-Phe-OH

[0346] ##STR00042##

[0347] Cbz-MeAla-Cys(Trt)-Ala-Phe-Phe-OSi(tBu).sub.2(Bn) (0.10 g, 0.08 mmol) was dissolved in methanol (4.0 g) at room temperature, potassium fluoride (0.05 g, 0.8 mmol) was added thereto and the mixture was stirred for 2 hours. The obtained reaction mixture was diluted with ethyl acetate, silica gel was added and the mixture was stirred and filtered. The obtained silica gel was washed with methanol, and then, the washed solution was concentrated to obtain Cbz-MeAla-Cys(Trt)-Ala-Phe-Phe-OH (0.08 g, Yield: 100%) as a white solid.

[0348] MASS (ESI) m/z; 946.49 (MH)

Reference Synthetic Example 3: Synthesis of di-t-butyloctadecylsilane

[0349] ##STR00043##

[0350] Octadecyltrichlorosilane (22.5 g, 58.0 mmol) was mixed with n-heptane (237 mL), and 1.6M t-butyl lithium pentane solution (136 mL, 21.7 mmol) was added dropwise thereto at room temperature. The obtained reaction mixture was refluxed at 100 C., and after the distilling mixed solution (123 g) of pentane and heptane was taken out, and the mixture was stirred at 100 C. for 22 hours. The obtained reaction mixture was cooled to 0 C., isopropyl alcohol (1.9 g) was added thereto, diluted with hexane (50 mL), and then, washed with water (50 mL) and a saturated brine solution (25 mL) in this order, the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain di-t-butyloctadecylsilane (21.7 g, Yield: 91%) as a colorless liquid.

[0351] .sup.1H-NMR (CDCl.sub.3)

[0352] ppm: 0.57-0.64 (2H, m), 0.88 (3H, t, J=6.7 Hz), 1.00 (18H, s), 1.23-1.29 (30H, m), 1.39-1.49 (2H, m), 3.29 (1H, t, J=2.6 Hz)

Synthetic Example 32: Synthesis of H-Phe-OSi(tBu).SUB.2.(C.SUB.18.H.SUB.37.)

[0353] ##STR00044##

[0354] (i) di-t-butyloctadecylsilane (0.32 g, 8.02 mmol) was mixed with methylene chloride (2.0 g), the mixture was cooled to 0 C., trifluoromethanesulfonic acid (0.12 g, 8.02 mmol) was added thereto, and then, the mixture was stirred at room temperature for 1 hour. The obtained reaction mixture was cooled to 0 C., a methylene chloride (2.0 g) solution Cbz-Phe-OH (0.20 g, 6.68 mmol) and imidazole (0.07 g, 10.2 mmol) was added dropwise thereto and the mixture was stirred at room temperature for 20 hours. The obtained reaction mixture was diluted with chloroform, and then, washed with an aqueous saturated ammonium chloride solution (20.0 g) and water in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.42 g, Yield: 89%) as a colorless liquid.

[0355] MASS (ESI+) m/z; 694.52 (M+H)+

[0356] (ii) Cbz-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.11 g, 1.58 mmol) was mixed with 2,2,2-trifluoroethanol (2.0 g) and methylene chloride (2.0 g), 10% by mass PdC (11.9 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at room temperature for 20 hours. After filtering the reaction mixture, the obtained filtrate was concentrated to obtain H-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.08 g, Yield: 97%) as a colorless oil.

[0357] MASS (ESI+) m/z; 560.48 (M+H)+

Synthetic Example 33: Synthesis of Boc-Phe-Phe-Phe-OSi(tBu).SUB.2.(C.SUB.18.H.SUB.37.)

[0358] ##STR00045##

[0359] (i) H-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (1.00 g, 1.79 mmol) was dissolved in methylene chloride (20.2 g), Cbz-Phe-OH (0.64 g, 2.15 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (0.42 g, 2.15 mmol) were added thereto under ice-cooling and the mixture was stirred for 1 hour. The obtained reaction mixture was diluted with chloroform, and then, washed with an aqueous saturated ammonium chloride solution and an aqueous saturated sodium hydrogen carbonate solution in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (1.47 g, Yield: 98%) as a white solid.

[0360] MASS (ESI+) m/z; 841.59 (M+H)+

[0361] (ii) Cbz-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (1.05 g, 1.25 mmol) was mixed with 2,2,2-trifluoroethanol (5.1 g) and methylene chloride (5.0 g), 10% by mass PdC (0.20 g) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at room temperature for 27 hours. After filtering the reaction mixture, the obtained filtrate was concentrated. The concentrate was dissolved in chloroform, water was added thereto and the liquids were separated. The organic layer was concentrated to obtain H-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.82 g, Yield: 94%) as a colorless oil.

[0362] MASS (ESI+) m/z; 707.55 (M+H)+

[0363] (iii) H-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.77 g, 1.09 mmol) and Boc-Phe-OH (0.58 g, 2.18 mmol) were dissolved in methylene chloride (16.0 g), 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide hydrochloride (0.42 g, 2.18 mmol) was added thereto under ice-cooling and the mixture was stirred at room temperature for 15 hours. The obtained reaction mixture was diluted with chloroform, and then, washed with an aqueous saturated sodium hydrogen carbonate solution and an aqueous saturated ammonium chloride solution in this order. The obtained organic layer was dried over magnesium sulfate, and then, the solution obtained by filtration was concentrated. The obtained residue was purified by silica gel column chromatography to obtain Boc-Phe-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.99 g, Yield: 91%) as a white solid.

[0364] MASS (ESI+) m/z; 954.67 (M+H)+

Synthetic Example 34: Synthesis of Fmoc-Phe-Phe-Phe-Phe-OSi(tBu).SUB.2.(C.SUB.18.H.SUB.37.)

[0365] ##STR00046##

[0366] (i) Boc-Phe-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.59 g, 0.62 mmol) was mixed with methylene chloride (12.0 g), the mixture was cooled to 0 C., 15% by mass hydrogen chloride-1,4-dioxane (3.1 g, 10.5 mmol) was added thereto and the mixture was stirred for 1 hour, and then, the mixture was returned to room temperature and stirred for 2 hours. The obtained reaction mixture was diluted with chloroform, and washed with an aqueous saturated sodium hydrogen carbonate solution and an aqueous saturated sodium chloride solution in this order. The obtained organic layer was concentrated to obtain H-Phe-Phe-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.15 g, Yield: 96%) as a white solid.

[0367] MASS (ESI+) m/z; 854.62 (M+H)+

[0368] (ii) H-Phe-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.50 g, 0.59 mmol) and Fmoc-Phe-OH (0.27 g, 0.70 mmol) were mixed with methylene chloride (10.0 g), the mixture was cooled to 0 C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.14 g, 0.73 mmol) was added thereto and the mixture was stirred for 1 hour. After returning to room temperature and stirring for 1 hour, the obtained reaction mixture was diluted with chloroform, and then, washed with an aqueous saturated sodium hydrogen carbonate solution and an aqueous saturated ammonium chloride solution in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Phe-Phe-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.67 g, Yield: 94%) as a white solid.

[0369] MASS (ESI+) m/z; 1223.76 (M+H)+

Synthetic Example 35: Synthesis of Cbz-Phe-Phe-Phe-Phe-Phe-OSi(tBu).SUB.2.(C.SUB.18.H.SUB.37.)

[0370] ##STR00047##

[0371] (i) Fmoc-Phe-Phe-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.40 g, 0.33 mmol) was mixed with methylene chloride (8.0 g), the mixture was cooled to 0 C., and diethylamine (0.72 g, 9.8 mmol) was added thereto. After returning to room temperature and stirring for 5 hours, the obtained reaction mixture was diluted with chloroform and washed with an aqueous saturated ammonium chloride solution, and the liquids were separated. The obtained organic layer was concentrated to obtain H-Phe-Phe-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.32 g, Yield: 96%) as a white solid.

[0372] MASS (ESI+) m/z; 1001.69 (M+H)+

[0373] (ii) H-Phe-Phe-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.25 g, 0.25 mmol) and Cbz-Phe-OH (0.09 g, 0.30 mmol) were mixed with methylene chloride (15.0 g), the mixture was cooled to 0 C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.06 g, 0.31 mmol) was added thereto and the mixture was stirred for 1 hour. After returning to room temperature and stirring for 1 hour, methanol (45.0 g) was added to the obtained reaction mixture to cause precipitation followed by filtration to obtain Cbz-Phe-Phe-Phe-Phe-Phe-OSi(tBu).sub.2(C.sub.18H.sub.37) (0.31 g, Yield: 95%) as a white solid.

[0374] MASS (ESI+) m/z; 1282.79 (M+H)+

Reference Synthetic Example 4: Synthesis of HSi(tBu).SUB.2.(OCH.SUB.2.CH.SUB.2.Ph)

[0375] ##STR00048##

[0376] 2-Phenylethyl alcohol (4.10 g, 33.6 mmol) was mixed with methylene chloride (10 g), triethylamine(5.66 g, 55.9 mmol), N,N-dimethyl-4-aminopyridine (0.69 g, 5.67 mmol) and di-tert-butylchlorosilane (5.01 g, 28.0 mmol) were added to the mixture at 0 C. and the mixture was stirred at room temperature for 15 hours. To the obtained reaction mixture were added an aqueous saturated sodium hydrogen carbonate solution (20 g) at 0 C. and the liquids were separated. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain di-t-butyl(2-phenylethyloxy)silane (6.62 g, Yield: 89%) as a colorless liquid.

[0377] .sup.1H-NMR (CDCl.sub.3)

[0378] ppm: 0.97 (18H, s), 2.87 (2H, d, J=7.4 Hz), 3.94 (2H, d, J=7.4 Hz), 3.97 (1H, s), 7.16-7.31 (5H, m)

Synthetic Example 36: Synthesis of H-Phe-OSi(tBu).SUB.2.(OCH.SUB.2.CH.SUB.2.Ph)

[0379] ##STR00049##

[0380] (i) Cbz-Phe-OH (4.25 g, 14.2 mmol) and di-t-butyl(2-phenylethyloxy)silane (2.52 g, 9.51 mmol) were mixed with N,N-dimethylformamide (25 g), zinc chloride (0.27 g, 2.0 mmol) was added thereto and the mixture was stirred at 60 C. for 30 minutes. Zinc chloride (0.27 g, 2.0 mmol) was added to the reaction mixture and the mixture was stirred at 120 C. for 20 hours. To the obtained reaction mixture were added 5% by mass aqueous sodium chloride solution (20 g) and ethyl acetate(32 g) at room temperature and the liquids were separated. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (1.53 g, Yield: 29%) as a colorless liquid.

[0381] MASS (ESI+) m/z; 562.38 (M+H)+

[0382] (ii) Cbz-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.81 g, 1.4 mmol) was dissolved in 2,2,2-trifluoroethanol (11 g), 10% by mass PdC (77 mg, 0.07 mmol) was added thereto and the mixture was stirred under a hydrogen gas atmosphere for 3 hours. After filtering the reaction mixture, the obtained filtrate was concentrated. The obtained concentrate was purified by silica gel column chromatography to obtain H-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.437 g, Yield: 71%) as a colorless liquid.

[0383] MASS (ESI+) m/z; 428.39 (M+H)+

Synthetic Example 37: Synthesis of Boc-Asp(OBn)-Phe-Phe-OSi(tBu).SUB.2.(OCH.SUB.2.CH.SUB.2.Ph)

[0384] ##STR00050##

[0385] (i) Cbz-Phe-OH (0.58 g, 1.92 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.36 g, 1.90 mmol) were dissolved in methylene chloride (8.0 g), H-Phe-OSi(tBu).sub.2(OCHCH.sub.2Ph) (0.41 g, 0.95 mmol) was added thereto under ice-cooling and the mixture was stirred for 2 hours. The obtained reaction mixture was washed with 4% by mass hydrochloric acid (4.0 g) and an aqueous saturated sodium hydrogen carbonate solution (4.0 g) in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2PH) (0.678 g, Yield: 94%) as a white solid.

[0386] MASS (ESI+) m/z; 709.45 (M+H)+

[0387] (ii) Cbz-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.62 g, 0.87 mmol) was dissolved in 2,2,2-trifluoroethanol (12.5 g), 10% by mass PdC (60 mg, 0.05 mmol) was added thereto and the mixture was stirred under a hydrogen gas atmosphere for 1.5 hours. The reaction mixture was filtered and the obtained filtrate was concentrated to obtain H-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.50 g, Yield: 100%) as a brown oil.

[0388] MASS (ESI+) m/z; 575.39 (M+H)+

[0389] (iii) H-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.49 g, 0.85 mmol) and Boc-Asp(OBn)-OH (0.41 g, 1.28 mmol) were dissolved in methylene chloride (9.3 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.25 g, 1.28 mmol) was added thereto under ice-cooling and the mixture was stirred for 1 hour. The obtained reaction mixture was washed with 4% by mass hydrochloric acid (5.0 g) and an aqueous saturated sodium hydrogen carbonate solution (5.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Asp(OBn)-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.63 g, Yield: 84%) as a white solid.

[0390] MASS (ESI+) m/z; 880.53 (M+H)+

Synthetic Example 38: Synthesis of Fmoc-Gly-Asp(OBn)-Phe-Phe-OSi(tBu).SUB.2.(OCH.SUB.2.CH.SUB.2.Ph)

[0391] ##STR00051##

[0392] (i) Boc-Asp(OBn)-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.30 g, 0.34 mmol) was dissolved in methylene chloride (8.0 g), the mixture was cooled to 0 C., 15% by mass hydrogen chloride-1,4-dioxane (2.5 g, 9.6 mmol) was added thereto and the mixture was stirred for 24 hours. The obtained reaction mixture was diluted with water (3.0 g), and then, washed with an aqueous saturated sodium hydrogen carbonate solution (3.0 g) and an aqueous saturated sodium chloride solution (3.0 g) in this order. The obtained organic layer was concentrated to obtain H-Asp(OBn)-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.26 g, Yield: 99%) as a pale yellow liquid.

[0393] MASS (ESI+) m/z; 780.54 (M+H)+

[0394] (ii) H-Asp(OBn)-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.25 g, 0.32 mmol) and Fmoc-Gly-OH (0.14 g, 0.48 mmol) were dissolved in methylene chloride (4.7 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.09 g, 0.49 mmol) was added thereto under ice-cooling and the mixture was stirred for 1 hour. The obtained reaction mixture was washed with 4% by mass hydrochloric acid (2.5 g) and an aqueous saturated sodium hydrogen carbonate solution (2.5 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Gly-Asp(OBn)-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.30 g, Yield: 90%) as a white solid.

[0395] MASS (ESI+) m/z; 1059.70 (M+H)+

Synthetic Example 39: Synthesis of Fmoc-Lys(Cbz)-Gly-Asp(OBn)-Phe-Phe-OH

[0396] ##STR00052##

[0397] (i) Fmoc-Gly-Asp(OBn)-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.14 g, 0.14 mmol) was mixed with methylene chloride (2.8 g), diethylamine (0.21 g, 2.83 mmol) was added thereto at 0 C. and the mixture was stirred at 0 C. for 3 hours, and further, the mixture was returned to room temperature and stirred for 5 hours. To the obtained reaction mixture was added a saturated aqueous ammonium chloride solution (1.5 g), and the liquids were separated. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain H-Gly-Asp(OBn)-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.06 g, Yield: 49%) as a white solid.

[0398] MASS (ESI+) m/z; 837.46 (M+H)+

[0399] (ii) H-Gly-Asp(OBn)-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.05 g, 0.06 mmol), Fmoc-Lys(Cbz)-OH (0.05 g, 0.09 mmol) were dissolved in methylene chloride (1.3 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.02 g, 0.11 mmol) was added thereto under ice-cooling and the mixture was stirred for 1.5 hours. The obtained reaction mixture was washed with 4% by mass hydrochloric acid (1.0 g) and an aqueous saturated sodium hydrogen carbonate solution (1.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Lys(Cbz)-Gly-Asp(OBn)-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.041 g, Yield: 49%) as a white solid.

[0400] (iii) Fmoc-Lys(Cbz)-Gly-Asp(OBn)-Phe-Phe-OSi(tBu).sub.2(OCH.sub.2CH.sub.2Ph) (0.04 g, 0.03 mmol) was mixed with methanol (0.20 g) and tetrahydrofuran (0.67 g), potassium fluoride (9.4 mg, 0.16 mmol) was added thereto at 0 C. and the mixture was stirred for 3 hours. To the obtained reaction mixture were added water (2.0 g) and methylene chloride (2.0 g) and the liquids were separated. Methylene chloride (3.0 g) was added to the obtained aqueous layer to carry out extraction three times, and the organic layers were mixed. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Lys(Cbz)-Gly-Asp(OBn)-Phe-Phe-OH (0.024 g, Yield: 69%) as a white solid.

[0401] MASS (ESI+) m/z; 1059.55 (M+H)+

Synthetic Example 40: Synthesis of H-Phe-OSi(OtBu).SUB.3

[0402] ##STR00053##

[0403] (i) Cbz-Phe-OH (0.30 g, 1.00 mmol), tert-butanol (0.48 g) and pyridine (0.39 g, 4.9 mmol) were mixed, tetrachlorosilane (0.17 g, 1.0 mmol) was added thereto at 0 C. and the mixture was stirred for 2.5 hours. Pyridine (0.20 g, 2.5 mmol) and tetrachlorosilane (0.081 g, 0.48 mmol) were added thereto and the mixture was stirred for 15 hours. The obtained reaction mixture was diluted with chloroform, washed with 10% by mass aqueous ammonium chloride solution, water and 5% by mass aqueous sodium hydrogen carbonate solution in this order, and the organic layer was concentrated. The obtained residue was purified by silica gel column chromatography to obtain Cbz-Phe-OSi(OtBu).sub.3 (0.27 g, Yield: 49%) as a colorless oil.

[0404] MASS (ESI+) m/z; 546.2 (M+H)+

[0405] (ii) Cbz-Phe-OSi(OtBu).sub.3 (0.22 g, 0.40 mmol) was dissolved in 2,2,2-trifluoroethanol (2.2 g), 10% by mass PdC (66 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at room temperature for 2 hours, and at 35 C. for 3 hours. The reaction mixture was filtered and the obtained filtrate was concentrated to obtain H-Phe-OSi(OtBu).sub.3 (0.15 g, Yield: 90%) as a white liquid.

[0406] MASS (ESI+) m/z; 412.4 (M+H)+

Synthetic Example 41: Synthesis of Fmoc-Phe-Phe-Phe-OSi(OtBu).SUB.3

[0407] ##STR00054##

[0408] (i) H-Phe-OSi(OtBu).sub.3 (70 mg, 0.17 mmol) and Cbz-Phe-OH (76 mg, 0.25 mmol) were dissolved in methylene chloride (1.4 g), N,N-diisopropylcarbodiimide (32 mg, 0.25 mmol) was added thereto under ice-cooling and the mixture was stirred for 2 hours. The obtained reaction mixture was diluted with chloroform (3 mL), washed with 10% by mass aqueous ammonium chloride solution and 5% by mass aqueous sodium hydrogen carbonate solution, the liquids were separated, and the organic layer was concentrated. The obtained residue was purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OSi(OtBu).sub.3 (91 mg, Yield: 77%) as a white solid.

[0409] MASS (ESI+) m/z; 693.5 (M+H)+

[0410] (ii) Cbz-Phe-Phe-OSi(OtBu).sub.3 (0.090 g, 0.13 mmol) was dissolved in 2,2,2-trifluoroethanol (1.8 g), 10% by mass PdC (27 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at room temperature for 4.5 hours. Further, 10% by mass PdC (10 mg) was added thereto and the mixture was stirred for 2 hours. The reaction mixture was filtered and the obtained filtrate was concentrated to obtain H-Phe-Phe-OSi(OtBu).sub.3 (73 mg, Yield: 100%) as a colorless oil.

[0411] MASS (ESI+) m/z; 559.4 (M+H)+

[0412] (iii) H-Phe-Phe-OSi(OtBu).sub.3 (73 mg, 0.13 mmol) and Fmoc-Phe-OH (76 mg, 0.20 mmol) were dissolved in methylene chloride (1.5 g), 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide (30 mg, 0.19 mmol) was added thereto under ice-cooling, and the mixture was stirred for 30 minutes. The obtained reaction mixture was diluted with chloroform (3 mL), washed with 10% by mass aqueous ammonium chloride solution (1 mL), water (1 mL) and 5% by mass aqueous sodium hydrogen carbonate solution (1 mL) in this order, and the organic layer was concentrated. The obtained residue was purified by silica gel column chromatography to obtain Fmoc-Phe-Phe-Phe-OSi(OtBu).sub.3 (75 mg, Yield: 81%) as a colorless oil.

[0413] MASS (ESI+) m/z; 928.5 (M+H)+

Synthetic Example 42: Synthesis of Cbz-Lys(Boc)-Phe-Phe-Phe-OH

[0414] ##STR00055##

[0415] (i) To Fmoc-Phe-Phe-Phe-OSi(OtBu).sub.3 (63 mg, 0.068 mmol) were added methylene chloride (1.4 g) and diethylamine (0.11 g, 1.50 mmol), and the mixture was stirred at room temperature for 7 hours. The obtained reaction mixture was diluted with chloroform and washed with 10% by mass aqueous ammonium chloride solution, and the liquids were separated. The organic layer was concentrated and the obtained residue was purified by silica gel column chromatography to obtain H-Phe-Phe-Phe-OSi(OtBu).sub.3 (43 mg, Yield: 90%) as a pale yellow product.

[0416] MASS (ESI+) m/z; 706.6 (M+H)+

[0417] (ii) H-Phe-Phe-Phe-OSi(OtBu).sub.3 (40 mg, 0.057 mmol) and Cbz-Lys(Boc)-OH (32 mg, 0.084 mmol) were dissolved in methylene chloride (1.2 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (13 mg, 0.085 mmol) was added thereto under ice-cooling and the mixture was stirred for 1.5 hours. The obtained reaction mixture was diluted with chloroform and diluted with 10% by mass aqueous ammonium chloride solution and the liquids were separated. The organic layer was concentrated and the obtained residue was purified by silica gel column chromatography to obtain Cbz-Lys(Boc)-Phe-Phe-Phe-OSi(OtBu).sub.3 (55 mg, Yield: 90%) as a colorless oil.

[0418] MASS (ESI+) m/z; 1068.7 (M+H)+

[0419] (iii) Cbz-Lys(Boc)-Phe-Phe-Phe-OSi(OtBu).sub.3 (50 mg, 0.047 mmol) was mixed with methanol (0.35 g) and tetrahydrofuran (1.1 g), potassium fluoride (4.1 mg, 0.071 mmol) was added thereto under ice-cooling and the mixture was stirred for 3 hours. After raising the temperature to room temperature followed by stirring for 3.5 hours, the obtained reaction mixture was concentrated. The mixture was diluted with chloroform (3 mL), 10% by mass aqueous ammonium chloride solution (1 mL) was added thereto and the liquids were separated, and chloroform was added to the aqueous layer to carry out extraction. The organic layers were combined, concentrated and purified by silica gel column chromatography to obtain Cbz-Lys(Boc)-Phe-Phe-Phe-OH (29 mg, Yield: 76%) as a white solid.

[0420] MASS (ESI+) m/z; 822.4 (M+H)+

Reference Synthetic Example 5: Synthesis of di-t-butylphenylsilane

[0421] ##STR00056##

[0422] Di-tert-butylchlorosilane (1.0 g, 5.6 mmol) was mixed with tetrahydrofuran (5.0 g), 1.6M phenyl lithium butyl ether solution (4.3 mL, 6.9 mmol) was added dropwise thereto at 0 C., and the mixture was stirred at 40 C. for 4 hours. To the obtained reaction mixture were added water (7.0 g) and hexane, and the liquids were separated and the aqueous layer was again extracted with hexane. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain di-t-butylphenylsilane (1.15 g, Yield: 94%) as a colorless liquid.

[0423] .sup.1H-NMR (CDCl.sub.3)

[0424] ppm: 1.04-1.06 (18H, br), 3.86 (1H, s), 7.29-7.39 (3H, m), 7.55-7.59 (2H, m)

Synthetic Example 43: Synthesis of Cbz-Phe-OSi(tBu).SUB.2.(Ph)

[0425] ##STR00057##

[0426] (i) Cbz-Phe-OH (0.54 g, 1.81 mmol) and di-t-butylphenylsilane (0.48 g, 2.18 mmol) were mixed with tetrahydrofuran (5.43 g), palladium acetate (122 mg, 0.54 mmol) was added thereto at room temperature and the mixture was stirred for 65 hours. The obtained reaction mixture was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-OSi(tBu).sub.2(Ph) (0.17 g, Yield: 18%) as a colorless liquid.

[0427] MASS (ESI+) m/z; 518.3 (M+H)+

[0428] (ii) Cbz-Phe-OSi(tBu).sub.2(Ph) (98 mg, 0.19 mmol) was dissolved in 2,2,2-trifluoroethanol (1.2 g), 10% by mass PdC (8.2 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at 30 C. for 2 hours. The reaction mixture was filtered and the obtained filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain H-Phe-OSi(tBu).sub.2(Ph) (72 mg, Yield: 100%) as a colorless liquid.

[0429] MASS (ESI+) m/z; 384.3 (M+H)+

Synthetic Example 44: Synthesis of Boc-Phe-Phe-Phe-OSi(tBu).SUB.2.(Ph)

[0430] ##STR00058##

[0431] (i) H-Phe-OSi(tBu).sub.2(Ph) (70 mg, 0.18 mmol) and Cbz-Phe-OH (82 mg, 0.27 mmol) were dissolved in methylene chloride (1.5 g), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (53 mg, 0.84 mmol) was added thereto under ice-cooling and the mixture was stirred for 1 hour. The obtained reaction mixture was diluted with chloroform (2 mL), water (2 mL) and 5% by mass aqueous sodium hydrogen carbonate solution (1 mL) were added thereto and the liquids were separated. The aqueous layer was again extracted with chloroform (1 mL), and the organic layer was concentrated. The obtained residue was purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OSi(tBu).sub.2(Ph) (0.11 g, Yield: 93%) as a colorless oil.

[0432] MASS (ESI+) m/z; 665.5 (M+H)+

[0433] (ii) Cbz-Phe-Phe-OSi(tBu).sub.2(Ph) (0.11 g, 0.17 mmol) was dissolved in 2,2,2-trifluoroethanol (1.1 g), 10% by mass PdC (11 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at 35 C. for 3 hours. 10% by mass PdC (22 mg) was added thereto and the mixture was stirred at 38 C. for 2 hours. 10% by mass PdC (22 mg) was added thereto and stirred at room temperature for 18 hours, then, the reaction mixture was filtered and the obtained filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain H-Phe-Phe-OSi(tBu).sub.2(Ph) (88 mg, Yield: 100%) as a colorless oil.

[0434] MASS (ESI+) m/z; 531.4 (M+H)+

[0435] (iii) H-Phe-Phe-OSi(tBu).sub.2(Ph) (88 mg, 0.17 mmol) and Boc-Phe-OH (66 mg, 0.25 mmol) were dissolved in methylene chloride (1.8 g), 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide hydrochloride (48 mg, 0.25 mmol) was added thereto under ice-cooling and the mixture was stirred at room temperature for 2 hours. Boc-Phe-OH (22 mg, 0.083 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (16 mg, 0.08 mmol) were added thereto, and the mixture was stirred at room temperature for 1.5 hours. The obtained reaction mixture was diluted with chloroform (2 mL), washed with 5% by mass aqueous sodium hydrogen carbonate solution (1 mL) and water (1 mL) in this order, and the organic layer was concentrated. The obtained residue was purified by silica gel column chromatography to obtain Boc-Phe-Phe-Phe-OSi(tBu).sub.2(Ph) (0.13 g, Yield: 100%) as a white solid.

[0436] MASS (ESI+) m/z; 778.4 (M+H)+

Synthetic Example 45: Synthesis of Fmoc-Gly-Phe-Phe-Phe-OSi(tBu).SUB.2.(Ph)

[0437] ##STR00059##

[0438] (i) Boc-Phe-Phe-Phe-OSi(tBu).sub.2(Ph) (0.13 g, 0.17 mmol) was mixed with methylene chloride (2.6 g), the mixture was cooled to 0 C., 15% by mass hydrogen chloride-1,4-dioxane (1.29 g) was added thereto and the mixture was stirred at room temperature for 2 hours. To the obtained reaction mixture was added 5% by mass aqueous sodium hydrogen carbonate solution, the mixture was neutralized and the liquids were separated, and the organic layer was further washed with water (1.0 g). The obtained organic layer was concentrated to obtain H-Phe-Phe-Phe-OSi(tBu).sub.2(Ph) (0.11 g, Yield: 99%) as a white solid.

[0439] MASS (ESI+) m/z; 678.5 (M+H)+

[0440] (ii) H-Phe-Phe-Phe-OSi(tBu).sub.2(Ph) (0.11 g, 0.17 mmol) and Fmoc-Gly-OH (74 mg, 0.25 mmol) were dissolved in methylene chloride (2.2 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (48 mg, 0.25 mmol) was added thereto under ice-cooling and the mixture was stirred for 0.5 hour. The obtained reaction mixture was diluted with chloroform (2 mL) and washed with 5% by mass aqueous sodium hydrogen carbonate solution (2 mL) and water (1 mL) in this order, and the organic layer was concentrated. The obtained residue was purified by silica gel column chromatography to obtain Fmoc-Gly-Phe-Phe-Phe-OSi(tBu).sub.2(Ph) (0.11 g, Yield: 71%) as a white solid.

[0441] MASS (ESI+) m/z; 957.6 (M+H)+

Reference Synthetic Example 6: Synthesis of IPBS-OTf

[0442] ##STR00060##

[0443] Di-i-propyl-t-butylsilane (2.59 g, 15.0 mmol) was dissolved in methylene chloride (10.0 g), trifluoromethanesulfonic acid (2.26 g, 15.0 mmol) was added dropwise thereto under ice-cooling and the mixture was stirred for 30 minutes. The formed di-i-propyl-t-butylsilyltriflate (4.82 g, 15.0 mmol) was used in the next reaction as a methylene chloride solution without isolation.

Synthetic Example 46: Synthesis of Cbz-Phe-OIPBS

[0444] ##STR00061##

[0445] (i) Cbz-Phe-OH (3.00 g, 10.0 mmol) and di-i-propyl-t-butylsilyltriflate (4.82 g, 15.0 mmol) were mixed with methylene chloride (49.9 g), the mixture was cooled to 0 C., N,N-diisopropylethylamine (2.59 g, 20.1 mmol) was added dropwise thereto, and the mixture was stirred at room temperature for 2 hours. The obtained reaction mixture was washed with an aqueous saturated ammonium chloride solution (35.9 g), then, washed with an aqueous saturated sodium hydrogen carbonate solution (40.0 g), and the obtained organic layer was concentrated to obtain Cbz-Phe-OIPBS (5.43 g) as a crude product.

[0446] MASS (ESI+) m/z; 471.2 (M+H)+

[0447] (ii) Cbz-Phe-OIPBS (5.43 g) was mixed with 2,2,2-trifluoroethanol (34.8 g), 10% by mass PdC (0.53 g, 0.50 mmol) and triethylsilane (4.66 g, 40.1 mmol) were added thereto and the mixture was stirred at room temperature for 2 hours. The reaction mixture was filtered, the obtained filtrate was concentrated, and then, the concentrate was purified by silica gel column chromatography to obtain H-Phe-OIPBS (3.26 g, 2-Step Yield: 97%) as a colorless liquid.

[0448] MASS (ESI+) m/z; 336.4 (M+H)+

Synthetic Example 47: Synthesis of Fmoc-Phe-Phe-Phe-OIPBS

[0449] ##STR00062##

[0450] (i) H-Phe-OIPBS (0.50 g, 1.49 mmol) was dissolved in methylene chloride (9.9 g), Cbz-Phe-OH (0.67 g, 2.24 mmol) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (0.43 g, 2.24 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (20.1 g) and water (20.0 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (24.5 g) and an aqueous saturated sodium chloride solution (14.9 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OIPBS (0.88 g, Yield: 95%) as a colorless liquid.

[0451] MASS (ESI+) m/z; 617.6 (M+H)+

[0452] (ii) Cbz-Phe-Phe-OIPBS (0.87 g, 1.41 mmol) was mixed with 2,2,2-trifluoroethanol (9.8 g), 10% by mass PdC (0.075 g, 0.071 mmol) and triethylsilane (0.66 g, 5.64 mmol) were added thereto and the mixture was stirred at room temperature for 3 hours. The reaction mixture was filtered, and the obtained filtrate was concentrated to obtain H-Phe-Phe-OIPBS (1.14 g) as a crude product.

[0453] MASS (ESI+) m/z; 483.5 (M+H)+

[0454] (iii) H-Phe-Phe-OIPBS (1.14 g) was dissolved in methylene chloride (9.4 g), Fmoc-Phe-OH (0.71 g, 1.83 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.35 g, 1.83 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (27.3 g) and water (25.1 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (29.0 g) and an aqueous saturated sodium chloride solution (20.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Phe-Phe-Phe-OIPBS (1.05 g, 2-Step Yield: 87%) as a white solid.

[0455] MASS (ESI+) m/z; 852.7 (M+H)+

Synthetic Example 48: Synthesis of Boc-Phe-Phe-Phe-Phe-OIPBS

[0456] ##STR00063##

[0457] (i) Fmoc-Phe-Phe-Phe-OIPBS (0.74 g, 0.87 mmol) was mixed with methylene chloride (7.7 g) at room temperature, diethylamine (0.64 g, 8.70 mmol) was added thereto and the mixture was stirred for 2 hours. After adding 8% by mass aqueous hydrogen chloride solution (3.0 g) to the reaction mixture, it was diluted with methylene chloride (27.4 g) and the liquids were separated. The organic layer was washed with an aqueous saturated sodium chloride solution (13.5 g), and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain H-Phe-Phe-Phe-OIPBS (0.51 g, Yield: 94%) as a white solid.

[0458] MASS (ESI+) m/z; 630.5 (M+H)+

[0459] (ii) H-Phe-Phe-Phe-OIPBS (0.51 g, 0.82 mmol) was dissolved in methylene chloride (5.4 g), Boc-Phe-OH (0.24 g, 0.90 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (0.17 g, 0.90 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (26.6 g) and water (11.2 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (19.6 g), an aqueous saturated sodium chloride solution (12.2 g) in this order, the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Phe-Phe-Phe-Phe-OIPBS (0.64 g, Yield: 89%) as a white solid.

[0460] MASS (ESI+) m/z; 877.8 (M+H)+

Synthetic Example 49: Synthesis of Cbz-Phe-Phe-Phe-Phe-Phe-OIPBS

[0461] ##STR00064##

[0462] (i) Boc-Phe-Phe-Phe-Phe-OIPBS (0.64 g, 0.73 mmol) was dissolved in methylene chloride (4.8 g), 15% by mass hydrogen chloride-1,4-dioxane (5.46 g, 21.8 mmol) was added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, the obtained reaction mixture was concentrated and subjected to azeotropic distillation with toluene (9.8 g) twice to obtain H-Phe-Phe-Phe-Phe-OIPBS hydrochloride (0.60 g) as a crude product.

[0463] MASS (ESI+) m/z; 778.6 (M+HHCl)+

[0464] (ii) H-Phe-Phe-Phe-Phe-OIPBS hydrochloride (0.10 g) was dissolved in methylene chloride (1.6 g), Cbz-Phe-OH (0.041 g, 0.14 mmol), O-(7-azabenzotriazol-1-yl)-N,N,N,N-tetramethyluronium hexafluorophosphate (0.051 g, 0.14 mmol) and N,N-diisopropylethylamine (0.024 g, 0.18 mmol) were added thereto under ice-cooling and the mixture was stirred for 30 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (13.3 g) and 10% by mass aqueous citric acid solution (5.4 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (11.6 g) and an aqueous saturated sodium chloride solution (7.3 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-Phe-Phe-Phe-OIPBS (0.11 g, 2-Step Yield: 86%) as a white solid.

[0465] MASS (ESI+) m/z; 1060.0 (M+H)+

Reference Synthetic Example 7: Synthesis of IPCS-OTf

[0466] ##STR00065##

[0467] Di-i-propylcumylsilane (3.52 g, 15.0 mmol) was dissolved in methylene chloride (10.0 g), trifluoromethanesulfonic acid (2.26 g, 15.0 mmol) was added dropwise thereto under ice-cooling and the mixture was stirred for 30 minutes. The formed di-i-propylcumylsilyltriflate (5.75 g, 15.0 mmol) was used in the next reaction as a methylene chloride solution without isolation.

Synthetic Example 50: Synthesis of Cbz-Phe-OIPCS

[0468] ##STR00066##

[0469] (i) Cbz-Phe-OH (3.00 g, 10.0 mmol) and di-i-propylcumylsilyltriflate (5.75 g, 15.0 mmol) were mixed with methylene chloride (49.9 g), the mixture was cooled to 0 C., N,N-diisopropylethylamine (2.59 g, 20.1 mmol) was added dropwise thereto, and the mixture was stirred at room temperature for 2 hours. The obtained reaction mixture was washed with an aqueous saturated ammonium chloride solution (40.0 g), and then, washed with an aqueous saturated sodium hydrogen carbonate solution (40.0 g) and the obtained organic layer was concentrated to obtain Cbz-Phe-OIPCS (5.90 g) as a crude product.

[0470] MASS (ESI+) m/z; 533.1 (M+H)+

[0471] (ii) Cbz-Phe-OIPCS (5.90 g) was mixed with 2,2,2-trifluoroethanol (34.8 g), 10% by mass PdC (0.53 g, 0.50 mmol) and triethylsilane (4.66 g, 40.1 mmol) were added thereto and the mixture was stirred at room temperature for 3 hours. The reaction mixture was filtered, the obtained filtrate was concentrated and the concentrate was purified by silica gel column chromatography to obtain H-Phe-OIPCS (3.37 g, 2-Step Yield: 85%) as a colorless liquid.

[0472] MASS (ESI+) m/z; 399.4 (M+H)+

Synthetic Example 51: Synthesis of Fmoc-Phe-Phe-Phe-OIPCS

[0473] ##STR00067##

[0474] (i) H-Phe-OIPCS (0.50 g, 1.26 mmol) was dissolved in methylene chloride (8.4 g), Cbz-Phe-OH (0.57 g, 1.89 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.36 g, 1.89 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (19.7 g) and water (20.5 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (25.0 g) and an aqueous saturated sodium chloride solution (14.1 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OIPCS (0.85 g, Yield: 99%) as a colorless liquid.

[0475] MASS (ESI+) m/z; 679.6 (M+H)+

[0476] (ii) Cbz-Phe-Phe-OIPCS (0.85 g, 1.25 mmol) was mixed with 2,2,2-trifluoroethanol (8.7 g), 10% by mass PdC (0.066 g, 0.062 mmol) and triethylsilane (0.58 g, 4.99 mmol) were added thereto and the mixture was stirred at room temperature for 3 hours. The reaction mixture was filtered, and the obtained filtrate was concentrated to obtain H-Phe-Phe-OIPCS (0.98 g) as a crude product.

[0477] MASS (ESI+) m/z; 545.5 (M+H)+

[0478] (iii) H-Phe-Phe-OIPCS (0.98 g) was dissolved in methylene chloride (8.3 g), Fmoc-Phe-OH (0.63 g, 1.62 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.31 g, 1.62 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (26.6 g) and water (28.8 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (30.3 g) and an aqueous saturated sodium chloride solution (20.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Phe-Phe-Phe-OIPCS (1.07 g, 2-Step Yield: 94%) as a white solid.

[0479] MASS (ESI+) m/z; 915.0 (M+H)+

Synthetic Example 52: Synthesis of Boc-Phe-Phe-Phe-Phe-OIPCS

[0480] ##STR00068##

[0481] (i) Fmoc-Phe-Phe-Phe-OIPCS (0.83 g, 0.91 mmol) was mixed with methylene chloride (8.0 g) at room temperature, diethylamine (0.66 g, 9.06 mmol) was added thereto and the mixture was stirred for 2 hours. To the reaction mixture was added 8% by mass aqueous hydrogen chloride solution (3.0 g), and then, the mixture was diluted with methylene chloride (29.3 g) and the liquids were separated. The organic layer was washed with an aqueous saturated sodium chloride solution (16.0 g), and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain H-Phe-Phe-Phe-OIPCS (0.54 g, Yield: 86%) as a white solid.

[0482] MASS (ESI+) m/z; 692.6 (M+H)+

[0483] ii) H-Phe-Phe-Phe-OIPCS (0.54 g, 0.78 mmol) was dissolved in methylene chloride (5.2 g), Boc-Phe-OH (0.23 g, 0.86 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.16 g, 0.86 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (18.7 g) and water (15.0 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (16.3 g), an aqueous saturated sodium chloride solution (13.8 g) in this order, the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Phe-Phe-Phe-Phe-OIPCS (0.59 g, Yield: 81%) as a white solid.

[0484] MASS (ESI+) m/z; 939.9 (M+H)+

Synthetic Example 53: Synthesis of Cbz-Phe-Phe-Phe-Phe-Phe-OIPCS

[0485] ##STR00069##

[0486] (i) Boc-Phe-Phe-Phe-Phe-OIPCS (0.59 g, 0.63 mmol) was dissolved in methylene chloride (4.1 g), 15% by mass hydrogen chloride-1,4-dioxane (4.74 g, 19.0 mmol) was added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, the obtained reaction mixture was concentrated and subjected to azeotropic distillation with toluene (8.7 g) twice to obtain H-Phe-Phe-Phe-Phe-OIPCS hydrochloride (0.56 g) as a crude product.

[0487] MASS (ESI+) m/z; 840.6 (M+HHCl)+

[0488] (ii) H-Phe-Phe-Phe-Phe-OIPCS hydrochloride (0.10 g) was dissolved in methylene chloride (1.5 g), Cbz-Phe-OH (0.038 g, 0.13 mmol), O-(7-azabenzotriazol-1-yl)-N,N,N,N-tetramethyluronium hexafluorophosphate (0.048 g, 0.13 mmol) and N,N-diisopropylethylamine (0.022 g, 0.17 mmol) were added thereto under ice-cooling and the mixture was stirred for 30 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (15.4 g) and 10% by mass aqueous citric acid solution (6.8 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (12.0 g) and an aqueous saturated sodium chloride solution (8.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-Phe-Phe-Phe-OIPCS (0.12 g, 2-Step Yield: 93%) as a white solid.

[0489] MASS (ESI+) m/z; 1120.9 (M+H)+

Reference Synthetic Example 8: Synthesis of CPCS-OTf

[0490] ##STR00070##

[0491] Di-cyclopentylcumylsilane (2.00 g, 6.98 mmol) was dissolved in methylene chloride (4.6 g), trifluoromethanesulfonic acid (1.05 g, 6.98 mmol) was added dropwise thereto under ice-cooling and the mixture was stirred for 30 minutes. The formed di-cyclopentylcumylsilyltriflate (3.03 g, 6.98 mmol) was used in the next reaction as a methylene chloride solution without isolation.

Synthetic Example 54: Synthesis of Cbz-Phe-OCPCS

[0492] ##STR00071##

[0493] (i) Cbz-Phe-OH (1.39 g, 4.65 mmol) and di-cyclopentylcumylsilyltriflate (3.03 g, 6.98 mmol) were mixed with methylene chloride (23.3 g), the mixture was cooled to 0 C., N,N-diisopropylethylamine (1.20 g, 9.31 mmol) was added dropwise thereto and the mixture was stirred at room temperature for 2 hours. The obtained reaction mixture was washed with an aqueous saturated ammonium chloride solution (21.1 g), and then, washed with an aqueous saturated sodium hydrogen carbonate solution (25.8 g), and the obtained organic layer was concentrated to obtain Cbz-Phe-OCPCS (3.05 g) as a crude product.

[0494] MASS (ESI+) m/z; 584.4 (M+H)+

[0495] (ii) Cbz-Phe-OCPCS (3.05 g) was mixed with 2,2,2-trifluoroethanol (12.9 g) and methylene chloride (3.1 g), 10% by mass PdC (0.50 g, 0.47 mmol) and triethylsilane (2.16 g, 18.6 mmol) were added thereto and the mixture was stirred at room temperature for 1 hour. The reaction mixture was filtered, the obtained filtrate was concentrated and the concentrate was purified by silica gel column chromatography to obtain H-Phe-OCPCS (1.91 g, 2-Step Yield: 91%) as a colorless liquid.

[0496] MASS (ESI+) m/z; 450.4 (M+H)+

Synthetic Example 55: Synthesis of Fmoc-Phe-Phe-Phe-OCPCS

[0497] ##STR00072##

[0498] (i) H-Phe-OCPCS (0.75 g, 1.67 mmol) was dissolved in methylene chloride (11.1 g), Cbz-Phe-OH (0.60 g, 2.00 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.38 g, 2.00 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (18.0 g) and water (24.1 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (20.5 g) and an aqueous saturated sodium chloride solution (18.4 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OCPCS (1.20 g, Yield: 99%) as a white liquid.

[0499] MASS (ESI+) m/z; 731.4 (M+H)+

[0500] (ii) Cbz-Phe-Phe-OCPCS (1.20 g, 1.64 mmol) was mixed with 2,2,2-trifluoroethanol (6.1 g) and methylene chloride (1.5 g), 10% by mass PdC (0.18 g, 0.16 mmol) and triethylsilane (0.76 g, 6.57 mmol) were added thereto and the mixture was stirred at room temperature for 1 hour. The reaction mixture was filtered, and the obtained filtrate was concentrated to obtain H-Phe-Phe-OCPCS (1.49 g) as a crude product.

[0501] MASS (ESI+) m/z; 597.4 (M+H)+

[0502] (iii) H-Phe-Phe-OCPCS (1.49 g) was dissolved in methylene chloride (10.9 g), Fmoc-Phe-OH (0.76 g, 1.97 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.38 g, 1.97 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (34.7 g) and water (30.0 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (29.0 g) and an aqueous saturated sodium chloride solution (17.7 g) in this order, and the organic layer was concentrated. The obtained solid was washed with 40% by mass ethyl acetate/hexane solution twice to obtain Fmoc-Phe-Phe-Phe-OCPCS (1.50 g, 2-Step Yield: 95%) as a white solid.

[0503] MASS (ESI+) m/z; 966.9 (M+H)+

Synthetic Example 56: Synthesis of Boc-Phe-Phe-Phe-Phe-OCPCS

[0504] ##STR00073##

[0505] (i) Fmoc-Phe-Phe-Phe-OCPCS (1.25 g, 1.29 mmol) was mixed with methylene chloride (17.2 g) at room temperature, diethylamine (0.95 g, 12.9 mmol) was added thereto and the mixture was stirred for 3 hours. To the reaction mixture was added 8% by mass aqueous hydrogen chloride solution (5.0 g), the mixture was diluted with methylene chloride (37.4 g) and the liquids were separated. The organic layer was washed with an aqueous saturated sodium chloride solution (19.5 g), and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain H-Phe-Phe-Phe-OCPCS (0.84 g, Yield: 87%) as a white solid.

[0506] MASS (ESI+) m/z; 744.5 (M+H)+

[0507] ii) H-Phe-Phe-Phe-OCPCS (0.84 g, 1.12 mmol) was dissolved in methylene chloride (7.5 g), Boc-Phe-OH (0.33 g, 1.24 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (0.24 g, 1.24 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (26.6 g) and water (18.0 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (22.4 g) and an aqueous saturated sodium chloride solution (15.2 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Phe-Phe-Phe-Phe-OCPCS (1.01 g, Yield: 91%) as a white solid.

[0508] MASS (ESI+) m/z; 991.7 (M+H)+

Synthetic Example 57: Synthesis of Cbz-Phe-Phe-Phe-Phe-Phe-OCPCS

[0509] ##STR00074##

[0510] (i) Boc-Phe-Phe-Phe-Phe-OCPCS (0.90 g, 0.91 mmol) was dissolved in methylene chloride (6.0 g), 15% by mass hydrogen chloride-1,4-dioxane (6.8 g, 27.2 mmol) was added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 90 minutes, the obtained reaction mixture was concentrated and subjected to azeotropic distillation with toluene (7.0 g) twice to obtain H-Phe-Phe-Phe-Phe-OCPCS hydrochloride (0.87 g) as a crude product.

[0511] MASS (ESI+) m/z; 891.6 (M+HHCl)+

[0512] (ii) H-Phe-Phe-Phe-Phe-OCPCS hydrochloride (0.10 g) was dissolved in methylene chloride (0.7 g) and N,N-dimethylformamide (0.5 g), Cbz-Phe-OH (0.036 g, 0.12 mmol), O-(7-azabenzotriazol-1-yl)-N,N,N,N-tetramethyluronium hexafluorophosphate (0.045 g, 0.12 mmol) and N,N-diisopropylethylamine (0.028 g, 0.22 mmol) were added thereto under ice-cooling and the mixture was stirred for 30 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (14.0 g) and 8% by mass aqueous hydrogen chloride solution (7.0 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (13.2 g) and an aqueous saturated sodium chloride solution (10.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-Phe-Phe-Phe-OCPCS (0.091 g, 2-Step Yield: 72%) as a white solid.

[0513] MASS (ESI+) m/z; 1173.7 (M+H)+

Reference Synthetic Example 9: Synthesis of CHCS-OTf

[0514] ##STR00075##

[0515] Di-cyclohexylcumylsilane (2.00 g, 6.36 mmol) was dissolved in methylene chloride (5.3 g), trifluoromethanesulfonic acid (0.95 g, 6.36 mmol) was added dropwise thereto under ice-cooling and the mixture was stirred for 40 minutes. The formed di-cyclohexylcumylsilyltriflate (2.94 g, 6.36 mmol) was used in the next reaction as a methylene chloride solution without isolation.

Synthetic Example 58: Synthesis of Cbz-Phe-OCHCS

[0516] ##STR00076##

[0517] (i) Cbz-Phe-OH (1.27 g, 4.24 mmol) and di-cyclohexylcumylsilyltriflate (2.94 g, 6.36 mmol) were mixed with methylene chloride (26.6 g), the mixture was cooled to 0 C., N,N-diisopropylethylamine (1.10 g, 8.48 mmol) was added dropwise thereto and the mixture was stirred at room temperature for 2 hours. The obtained reaction mixture was washed with an aqueous saturated ammonium chloride solution (30.0 g), and then, washed with an aqueous saturated sodium hydrogen carbonate solution (30.0 g), and the obtained organic layer was concentrated to obtain Cbz-Phe-OCHCS (3.43 g) as a crude product.

[0518] MASS (ESI+) m/z; 612.5 (M+H)+

[0519] (ii) Cbz-Phe-OCHCS (3.43 g) was mixed with 2,2,2-trifluoroethanol (8.3 g) and methylene chloride (5.3 g), 10% by mass PdC (0.45 g, 0.42 mmol) and triethylsilane (2.96 g, 25.4 mmol) were added thereto and the mixture was stirred at room temperature for 4 hours. The reaction mixture was filtered, the obtained filtrate was concentrated and the concentrate was purified by silica gel column chromatography to obtain H-Phe-OCHCS (1.81 g, 2-Step Yield: 89%) as a colorless liquid.

[0520] MASS (ESI+) m/z; 478.4 (M+H)+

Synthetic Example 59: Synthesis of Fmoc-Phe-Phe-Phe-OCHCS

[0521] ##STR00077##

[0522] (i) H-Phe-OCHCS (0.60 g, 1.26 mmol) was dissolved in methylene chloride (8.0 g), Cbz-Phe-OH (0.45 g, 1.51 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.29 g, 1.51 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (8.0 g) and water (16.0 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (25.0 g) and an aqueous saturated sodium chloride solution (25.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OCHCS (0.87 g, Yield: 91%) as a colorless liquid.

[0523] MASS (ESI+) m/z; 759.5 (M+H)+

[0524] (ii) Cbz-Phe-Phe-OCHCS (0.87 g, 1.14 mmol) was mixed with 2,2,2-trifluoroethanol (4.2 g) and methylene chloride (2.7 g), 10% by mass PdC (0.12 g, 0.11 mmol) and triethylsilane (0.80 g, 6.85 mmol) were added thereto and the mixture was stirred at room temperature for 4 hours. The reaction mixture was filtered, and the obtained filtrate was concentrated to obtain H-Phe-Phe-OCHCS (0.94 g) as a crude product.

[0525] MASS (ESI+) m/z; 625.5 (M+H)+

[0526] (iii) H-Phe-Phe-OCHCS (0.94 g) was dissolved in methylene chloride (6.7 g), Fmoc-Phe-OH (0.49 g, 1.26 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.24 g, 1.26 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (6.7 g) and water (10.0 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (15.0 g) and an aqueous saturated sodium chloride solution (10.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Phe-Phe-Phe-OCHCS (0.84 g, 2-Step Yield: 74%) as a white solid.

[0527] MASS (ESI+) m/z; 994.7 (M+H)+

Synthetic Example 60: Synthesis of Boc-Phe-Phe-Phe-Phe-OCHCS

[0528] ##STR00078##

[0529] (i) Fmoc-Phe-Phe-Phe-OCHCS (0.70 g, 0.70 mmol) was mixed with methylene chloride (6.3 g) at room temperature, diethylamine (1.03 g, 14.0 mmol) was added thereto and the mixture was stirred for 4 hours. To the reaction mixture was added 8% by mass aqueous hydrogen chloride solution (10.0 g), the mixture was diluted with methylene chloride (6.7 g) and the liquids were separated. The organic layer was washed with an aqueous saturated sodium chloride solution (10.0 g), and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain H-Phe-Phe-Phe-OCHCS (0.30 g, Yield: 55%) as a white solid.

[0530] MASS (ESI+) m/z; 772.6 (M+H)+

[0531] (ii) H-Phe-Phe-Phe-OCHCS (0.060 g, 0.078 mmol) was dissolved in methylene chloride (2.7 g), Boc-Phe-OH (0.023 g, 0.085 mmol), O-(7-azabenzotriazol-1-yl)-N,N,N,N-tetramethyluronium hexafluorophosphate (0.033 g, 0.085 mmol) and N,N-diisopropylethylamine (0.014 g, 0.11 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (2.7 g) and water (10.0 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (15.0 g) and an aqueous saturated sodium chloride solution (10.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Phe-Phe-Phe-Phe-OCHCS (0.074 g, Yield: 94%) as a white solid.

[0532] MASS (ESI+) m/z; 1019.7 (M+H)+

Synthetic Example 61: Synthesis of Cbz-Phe-Phe-Phe-Phe-Phe-OCHCS

[0533] ##STR00079##

[0534] (i) Boc-Phe-Phe-Phe-Phe-OCHCS (0.074 g, 0.073 mmol) was dissolved in methylene chloride (2.7 g), 15% by mass hydrogen chloride-1,4-dioxane (2.0 g, 8.03 mmol) was added thereto under ice-cooling and the mixture was stirred for 10 minutes. After returning to room temperature and stirring for further 1 hour, the obtained reaction mixture was concentrated and subjected to azeotropic distillation with toluene (8.7 g) twice to obtain H-Phe-Phe-Phe-Phe-OCHCS hydrochloride (0.058 g) as a crude product.

[0535] MASS (ESI+) m/z; 919.7 (M+HHCl)+

[0536] (ii) H-Phe-Phe-Phe-Phe-OCHCS hydrochloride (0.058 g) was dissolved in methylene chloride (2.7 g), Cbz-Phe-OH (0.021 g, 0.069 mmol), O-(7-azabenzotriazol-1-yl)-N,N,N,N-tetramethyluronium hexafluorophosphate (0.026 g, 0.069 mmol) and N,N-diisopropylethylamine (0.016 g, 0.126 mmol) were added thereto under ice-cooling and the mixture was stirred for 10 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (2.7 g) and 10% by mass aqueous citric acid solution (10.0 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (10.0 g) and an aqueous saturated sodium chloride solution (10.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-Phe-Phe-Phe-OCHCS (0.040 g, 2-Step Yield: 54%) as a white solid.

[0537] MASS (ESI+) m/z; 1201.8 (M+H)+

Reference Synthetic Example 10: Synthesis of SBCS-OTf

[0538] ##STR00080##

[0539] Di-s-butylcumylsilane (2.00 g, 7.62 mmol) was dissolved in methylene chloride (5.1 g), trifluoromethanesulfonic acid (1.14 g, 7.62 mmol) was added dropwise thereto under ice-cooling and the mixture was stirred for 30 minutes. The formed di-s-butylcumylsilyltriflate (3.13 g, 7.62 mmol) was used in the next reaction as a methylene chloride solution without isolation.

Synthetic Example 62: Synthesis of Cbz-Phe-OSBCS

[0540] ##STR00081##

[0541] (i) Cbz-Phe-OH (1.52 g, 5.08 mmol) and di-s-butylcumylsilyltriflate (3.13 g, 7.62 mmol) were mixed with methylene chloride (25.3 g), the mixture was cooled to 0 C., N,N-diisopropylethylamine (1.31 g, 10.2 mmol) was added dropwise thereto and the mixture was stirred at room temperature for 2 hours. The obtained reaction mixture was washed with an aqueous saturated ammonium chloride solution (21.1 g), and then, washed with an aqueous saturated sodium hydrogen carbonate solution (25.8 g), and the obtained organic layer was concentrated to obtain Cbz-Phe-OSBCS (3.18 g) as a crude product.

[0542] MASS (ESI+) m/z; 560.4 (M+H)+

[0543] (ii) Cbz-Phe-OSBCS (3.18 g) was mixed with 2,2,2-trifluoroethanol (14.1 g) and methylene chloride (3.4 g), 10% by mass PdC (0.54 g, 0.51 mmol) and triethylsilane (2.36 g, 20.3 mmol) were added thereto and the mixture was stirred at room temperature for 1 hour. The reaction mixture was filtered, the obtained filtrate was concentrated, and the concentrate was purified by silica gel column chromatography to obtain H-Phe-OSBCS (2.05 g, 2-Step Yield: 95%) as a colorless liquid.

[0544] MASS (ESI+) m/z; 426.4 (M+H)+

Synthetic Example 63: Synthesis of Fmoc-Phe-Phe-Phe-OSBCS

[0545] ##STR00082##

[0546] (i) H-Phe-OSBCS (0.60 g, 1.41 mmol) was dissolved in methylene chloride (9.4 g), Cbz-Phe-OH (0.51 g, 1.69 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.32 g, 1.69 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (16.9 g), water (20.1 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (17.3 g) and an aqueous saturated sodium chloride solution (15.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OSBCS (0.94 g, Yield: 95%) as a colorless liquid.

[0547] MASS (ESI+) m/z; 707.5 (M+H)+

[0548] (ii) Cbz-Phe-Phe-OSBCS (0.94 g, 1.34 mmol) was mixed with 2,2,2-trifluoroethanol (4.9 g) and methylene chloride (1.2 g), 10% by mass PdC (0.14 g, 0.13 mmol) and triethylsilane (0.62 g, 5.34 mmol) were added thereto and the mixture was stirred at room temperature for 1 hour. The reaction mixture was filtered, and the obtained filtrate was concentrated to obtain H-Phe-Phe-OSBCS (1.05 g) as a crude product.

[0549] MASS (ESI+) m/z; 573.5 (M+H)+

[0550] (iii) H-Phe-Phe-OSBCS (1.05 g) was dissolved in methylene chloride (8.9 g), Fmoc-Phe-OH (0.62 g, 1.60 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.31 g, 1.60 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (22.4 g) and water (19.4 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (20.0 g) and an aqueous saturated sodium chloride solution (11.1 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Phe-Phe-Phe-OSBCS (1.22 g, 2-Step Yield: 97%) as a white solid.

[0551] MASS (ESI+) m/z; 942.7 (M+H)+

Synthetic Example 64: Synthesis of Boc-Phe-Phe-Phe-Phe-OSBCS

[0552] ##STR00083##

[0553] (i) Fmoc-Phe-Phe-Phe-OSBCS (1.00 g, 1.06 mmol) was mixed with methylene chloride (14.1 g) at room temperature, diethylamine (0.78 g, 10.6 mmol) was added thereto and the mixture was stirred for 3 hours. To the reaction mixture was added 8% by mass aqueous hydrogen chloride solution (6.0 g), the mixture was diluted with methylene chloride (26.6 g) and the liquids were separated. The organic layer was washed with an aqueous saturated sodium chloride solution (15.0 g), and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain H-Phe-Phe-Phe-OSBCS (0.62 g, Yield: 80%) as a white solid.

[0554] MASS (ESI+) m/z; 720.8 (M+H)+

[0555] ii) H-Phe-Phe-Phe-OSBCS (0.45 g, 0.63 mmol) was dissolved in methylene chloride (4.2 g), Boc-Phe-OH (0.18 g, 0.69 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (0.13 g, 0.69 mmol) were added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (13.3 g) and water (10.6 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (15.3 g) and an aqueous saturated sodium chloride solution (8.0 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Phe-Phe-Phe-Phe-OSBCS (0.58 g, Yield: 96%) as a white solid.

[0556] MASS (ESI+) m/z; 967.7 (M+H)+

Synthetic Example 65: Synthesis of Cbz-Phe-Phe-Phe-Phe-Phe-OSBCS

[0557] ##STR00084##

[0558] (i) Boc-Phe-Phe-Phe-Phe-OSBCS (0.58 g, 0.60 mmol) was dissolved in methylene chloride (4.0 g), 15% by mass hydrogen chloride-1,4-dioxane (4.5 g, 18.0 mmol) was added thereto under ice-cooling and the mixture was stirred for 20 minutes. After returning to room temperature and stirring for further 1 hour, the obtained reaction mixture was concentrated and subjected to azeotropic distillation with toluene (6.0 g) twice to obtain H-Phe-Phe-Phe-Phe-OSBCS hydrochloride (0.58 g) as a crude product.

[0559] MASS (ESI+) m/z; 867.6 (M+HHCl)+

[0560] (ii) H-Phe-Phe-Phe-Phe-OSBCS hydrochloride (0.10 g) was dissolved in methylene chloride (0.7 g) and N,N-dimethylformamide (0.5 g), Cbz-Phe-OH (0.036 g, 0.12 mmol), O-(7-azabenzotriazol-1-yl)-N,N,N,N-tetramethyluronium hexafluorophosphate (0.046 g, 0.12 mmol) and N,N-diisopropylethylamine (0.029 g, 0.22 mmol) were added thereto under ice-cooling and the mixture was stirred for 30 minutes. After returning to room temperature and stirring for further 1 hour, methylene chloride (11.8 g) and 8% by mass aqueous hydrogen chloride solution (6.1 g) were added thereto and the liquids were separated. The organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (12.0 g) and an aqueous saturated sodium chloride solution (9.7 g) in this order, and the obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-Phe-Phe-Phe-OSBCS (0.12 g, 2-Step Yield: 96%) as a white solid.

[0561] MASS (ESI+) m/z; 1148.8 (M+H)+

Synthetic Example 66: Synthesis of H-Phe-OSi(tBu).SUB.3

[0562] ##STR00085##

[0563] (i) Tri-tert-butylsilane (0.24 g, 1.2 mmol) was mixed with methylene chloride (4.0 g), the mixture was cooled to 0 C., trifluoromethanesulfonic acid (0.20 g, 1.3 mmol) was added dropwise thereto, and the mixture was stirred at room temperature for 1 hour. The obtained reaction mixture was cooled to 0 C., a methylene chloride (2.0 g) solution of Cbz-Phe-OH (0.40 g, 1.3 mmol) and imidazole (0.14 g, 2.1 mmol) was added dropwise thereto, and the mixture was stirred at 40 C. for 15 hours. The obtained reaction mixture was diluted with chloroform, and washed with 10% by mass aqueous ammonium chloride solution (2 mL) and water (2 mL) in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-OSi(tBu).sub.3(0.17 g, Yield: 28%) as a colorless liquid.

[0564] MASS (ESI+) m/z; 498.4 (M+H)+

[0565] (ii) Cbz-Phe-OSi(tBu).sub.3 (0.16 g, 0.32 mmol) was mixed with 2,2,2-trifluoroethanol (3.2 g), 10% by mass PdC (48 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at room temperature for 4 hours. After filtering the reaction mixture, the obtained filtrate was concentrated to obtain H-Phe-OSi(tBu).sub.3 (0.12 g, Yield: 100%) as a pale brownish liquid.

[0566] MASS (ESI+) m/z; 364.4 (M+H)+

##STR00086##

Synthetic Example 67: Synthesis of Boc-Ala-Val-Pro-Phe-OSi(tBu).SUB.3

[0567] (i) H-Phe-OSi(tBu).sub.3 (120 mg, 0.33 mmol) and Cbz-Val-Pro-OH (138 mg, 0.40 mmol) were dissolved in methylene chloride (2.4 g), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (76 mg, 0.40 mmol) was added to the mixture under ice-cooling and the mixture was stirred for 2 hours. The obtained reaction mixture was diluted with chloroform (3 mL), and then, washed with 10% by mass aqueous ammonium chloride solution (2 mL) and the liquids were separated, and the aqueous layer was again extracted with chloroform. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Val-Pro-Phe-OSi(tBu).sub.3 (218 mg, Yield: 95%) as a colorless liquid.

[0568] MASS (ESI+) m/z; 694.6 (M+H)+

[0569] (ii) Cbz-Val-Pro-Phe-OSi(tBu).sub.3 (0.19 g, 0.27 mmol) was mixed with 2,2,2-trifluoroethanol (3.8 g), 10% by mass PdC (57 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at room temperature for 3 hours. Further, 10% by mass PdC (19 mg) was added thereto and the mixture was stirred at room temperature for 17 hours. After filtering the reaction mixture, the obtained filtrate was concentrated to obtain H-Val-Pro-Phe-OSi(tBu).sub.3 (153 mg, Yield: 100%) as a brown solid.

[0570] MASS (ESI+) m/z; 560.5 (M+H)+

[0571] (iii) H-Val-Pro-Phe-OSi(tBu).sub.3 (138 mg, 0.25 mmol) and Boc-Ala-OH (56 mg, 0.30 mmol) were dissolved in methylene chloride (1.4 g), 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide hydrochloride (57 mg, 0.30 mmol) was added to the mixture under ice-cooling and the mixture was stirred for 1.5 hours. Further, Boc-Ala-OH (19 mg, 0.10 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (19 mg, 0.10 mmol) were added thereto, and the mixture was stirred for 7 hours. The obtained reaction mixture was diluted with chloroform, washed with 10% by mass aqueous ammonium chloride solution and 5% by mass aqueous sodium hydrogen carbonate solution in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Ala-Val-Pro-Phe-OSi(tBu).sub.3 (153 mg, Yield: 85%) as a white solid.

[0572] MASS (ESI+) m/z; 731.6 (M+H)+

Synthetic Example 68: Synthesis of H-Phe-Ala-Val-Pro-Phe-OSi(tBu).SUB.3

[0573] ##STR00087##

[0574] (i) Boc-Ala-Val-Pro-Phe-OSi(tBu).sub.3 (120 mg, 0.16 mmol) was mixed with methylene chloride (2.4 g), 15% by mass hydrogen chloride-1,4-dioxane (1.2 g) was added thereto and the mixture was stirred at room temperature for 23 hours. The obtained reaction mixture was concentrated to obtain H-Ala-Val-Pro-Phe-OSi(tBu).sub.3 hydrochloride (107 mg, Yield: 100%) as a white solid.

[0575] MASS (ESI+) m/z; 631 (M+H)+

[0576] (ii) H-Ala-Val-Pro-Phe-OSi(tBu).sub.3 hydrochloride (107 mg, 0.15 mmol), Fmoc-Phe-OH (69 mg, 0.18 mmol) and diisopropylethylamine (25 mg, 0.19 mmol) were dissolved in methylene chloride (1.4 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (34 mg, 0.18 mmol) were added thereto under ice-cooling and the mixture was stirred at room temperature for 2 hours. The obtained reaction mixture was diluted with chloroform, and then, washed with 10% by mass aqueous ammonium chloride solution and 5% by mass aqueous sodium hydrogen carbonate solution in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Phe-Ala-Val-Pro-Phe-OSi(tBu).sub.3 (146 mg, Yield: 99%) as a white solid.

[0577] MASS (ESI+) m/z; 1000 (M+H)+

[0578] (iii) Fmoc-Phe-Ala-Val-Pro-Phe-OSi(tBu).sub.3 (130 mg, 0.13 mmol) was mixed with methylene chloride (2.0 g), the mixture was cooled to 0 C., diethylamine (0.19 g, 2.6 mmol) was added thereto and the mixture was stirred at room temperature for 3 hours, and at 35 C. for 3 hours. After cooling to room temperature, the mixture was diluted with methylene chloride, and washed with 10% by mass aqueous ammonium chloride solution (2 mL) and water in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain H-Phe-Ala-Val-Pro-Phe-OSi(tBu).sub.3 (97 mg, Yield: 97%) as a white solid.

[0579] MASS (ESI+) m/z; 778 (M+H)+

Synthetic Example 69: Synthesis of Cbz-Phe-Phe-Ala-Val-Pro-Phe-OH

[0580] ##STR00088##

[0581] (i) H-Phe-Ala-Val-Pro-Phe-OSi(tBu).sub.3 (90 mg, 0.12 mmol) and Cbz-Phe-OH (42 mg, 0.14 mmol) were dissolved in methylene chloride (1.8 g), 1-ethyl-3-(3-dimethyl-aminopropyl)carbodiimide hydrochloride (27 mg, 0.14 mmol) was added thereto under ice-cooling and the mixture was stirred at room temperature for 0.5 hour. The obtained reaction mixture was diluted with chloroform, and then, washed with 10% by mass aqueous ammonium chloride solution and 5% by mass aqueous sodium hydrogen carbonate solution in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-Ala-Val-Pro-Phe-OSi(tBu).sub.3 (109 mg, Yield: 89%) as a white solid.

[0582] MASS (ESI+) m/z; 1059.7 (M+H)+

[0583] (ii) Cbz-Phe-Phe-Ala-Val-Pro-Phe-OSi(tBu).sub.3 (55 mg, 0.052 mmol) was mixed with methanol (0.28 g) and tetrahydrofuran (0.83 g), potassium fluoride (6.0 mg, 0.10 mmol) was added thereto at 0 C. and the mixture was stirred at 30 C. for 22 hours. Potassium fluoride (12 mg, 0.20 mmol) and methanol (1 mL) were added thereto, and the mixture was further stirred at 30 C. for 4 hours. The obtained reaction mixture was concentrated, and then, diluted with chloroform and washed with 5% by mass aqueous sodium chloride solution. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-Ala-Val-Pro-Phe-OH (39 mg, Yield: 88%) as a white solid.

[0584] MASS (ESI+) m/z; 861.5 (M+H)+

Synthetic Example 70: Synthesis of H-Phe-OSi(tBu).SUB.2.(CH.SUB.2.TMS)

[0585] ##STR00089##

[0586] (i) To a tetrahydrofuran (2.5 mL) solution of magnesium (0.17 g, 7.0 mmol) were added iodine (10 mg) and dibromoethane (10 L) and (chloromethyl)trimethylsilane (0.86 g, 7.0 mmol) was added dropwise thereto at 30 C., and the mixture was stirred at 65 C. for 2 hours. The obtained reaction mixture was cooled to room temperature, and then, it was added dropwise to a tetrahydrofuran (3 mL) solution of di-tert-butylchlorosilane (0.25 g, 1.4 mmol) and the mixture was stirred at 65 C. for 5 hours. The obtained reaction mixture was cooled to room temperature, diluted with hexane, and then, the liquids were separated by 10% by mass aqueous ammonium chloride solution and 5% by mass aqueous sodium chloride solution in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain di-tert-butylsilylmethyltrimethylsilane (0.24 g, Yield: 37%) as a colorless liquid.

[0587] .sup.1H-NMR (CDCl.sub.3)

[0588] ppm: 0.34 (2H, d, J=3.0 Hz), 0.07 (9H, s), 0.98 (18H, s), 3.42 (1H, m) (ii) Di-tert-butylsilylmethyltrimethylsilane (0.17 g, 0.74 mmol) and dichloromethane (2.0 g) were mixed, trifluoromethanesulfonic acid (0.11 g, 0.73 mmol) was added dropwise thereto under ice-cooling and the mixture was stirred at room temperature for 1 hour. The obtained reaction mixture was cooled to 0 C., then, a methylene chloride (2.0 g) solution of Cbz-Phe-OH (0.20 g, 0.67 mmol) and imidazole (91 mg, 1.3 mmol) was added dropwise thereto, and the mixture was stirred at room temperature for 2 hours. The obtained reaction mixture was diluted with chloroform, and washed with 10% by mass aqueous ammonium chloride solution (2 mL) and 5% by mass sodium hydrogen carbonate (2 mL) in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (0.10 g, Yield: 29%) as a colorless liquid.

[0589] MASS (ESI+) m/z; 528.4 (M+H)+

[0590] (iii) Cbz-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (95 mg, 0.18 mmol) was dissolved in 2,2,2-trifluoroethanol (1.9 g), 10% by mass PdC (29 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at 30 C. for 5 hours. The reaction mixture was filtered, and the obtained filtrate was concentrated to obtain H-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (71 mg, Yield: 100%) as a colorless liquid.

[0591] MASS (ESI+) m/z; 394.4 (M+H)+

Synthetic Example 71: Synthesis of Fmoc-Phe-Phe-Phe-OSi(tBu).SUB.2.(CH.SUB.2.TMS)

[0592] ##STR00090##

[0593] (i) H-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (71 mg, 0.18 mmol) and Cbz-Phe-OH (65 mg, 0.22 mmol) were mixed with methylene chloride (1.4 g), 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide hydrochloride (42 mg, 0.22 mmol) was added thereto and the mixture was stirred for 0.5 hour. The obtained reaction mixture was diluted with chloroform (3 mL), and then, washed with 10% by mass aqueous ammonium chloride solution (2 mL), 5% by mass aqueous sodium hydrogen carbonate solution (2 mL) in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Cbz-Phe-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (97 mg, Yield: 80%) as a colorless liquid.

[0594] MASS (ESI+) m/z; 675.5 (M+H)+

[0595] (ii) Cbz-Phe-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (81 mg, 0.12 mmol) was dissolved in 2,2,2-trifluoroethanol (1.6 g), 10% by mass PdC (24 mg) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at room temperature for 4 hours. The reaction mixture was filtered and the obtained filtrate was concentrated to obtain H-Phe-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (65 mg, Yield: 100%) as a brown solid.

[0596] MASS (ESI+) m/z; 541.4 (M+H)+

[0597] (iii), H-Phe-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (65 mg, 0.12 mmol) and Fmoc-Phe-OH (56 mg, 0.14 mmol) were dissolved in methylene chloride (1.3 g), 1-ethyl-3-(3-dimethyl-aminopropyl)carbodiimide hydrochloride (28 mg, 0.15 mmol) was added thereto under ice-cooling and the mixture was stirred for 30 minutes. The obtained reaction mixture was diluted with chloroform, and then, washed with 10% by mass aqueous ammonium chloride solution and 5% by mass aqueous sodium hydrogen carbonate solution in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Fmoc-Phe-Phe-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (99 mg, Yield: 100%) as a white solid.

[0598] MASS (ESI+) m/z; 822.5 (M+H)+

Synthetic Example 72: Synthesis of H-Phe-Phe-Phe-Phe-OSi(tBu).SUB.2.(CH.SUB.2.TMS)

[0599] ##STR00091##

[0600] (i) Fmoc-Phe-Phe-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (99 mg, 0.12 mmol) was mixed with methylene chloride (2.0 g), diethylamine (0.18 g, 2.5 mmol) was added thereto at room temperature and the mixture was stirred at 40 C. for 3 hours. After cooling to room temperature, the mixture was diluted with chloroform, 10% by mass aqueous ammonium chloride solution (3 mL) was added thereto and the liquids were separated. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain H-Phe-Phe-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (74 mg, Yield: 89%) as a white solid.

[0601] MASS (ESI+) m/z; 688.5 (M+H)+

[0602] (ii) H-Phe-Phe-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (55 mg, 0.08 mmol) and Boc-Phe-OH (25 mg, 0.094 mmol) were dissolved in methylene chloride (1.1 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (19 mg, 0.099 mmol) was added thereto under ice-cooling and the mixture was stirred for 30 minutes. The obtained reaction mixture was diluted with chloroform and washed with 5% by mass aqueous sodium hydrogen carbonate solution and water in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography to obtain Boc-Phe-Phe-Phe-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (74 mg, Yield: 99%) as a white solid.

[0603] MASS (ESI+) m/z; 935.7 (M+H)+

[0604] (iii) Boc-Phe-Phe-Phe-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (74 mg, 0.079 mmol) was dissolved in methylene chloride (1.5 g), 15% by mass hydrogen chloride-1,4-dioxane (0.74 g) was added thereto under ice-cooling and the mixture was stirred at room temperature for 4 hours. The obtained reaction mixture was diluted with chloroform and washed with 5% by mass aqueous sodium hydrogen carbonate solution and water in this order. The obtained organic layer was concentrated to obtain H-Phe-Phe-Phe-Phe-OSi(tBu).sub.2(CH.sub.2TMS) (65 mg, Yield: 98%) as a white solid.

[0605] MASS (ESI+) m/z; 835.6 (M+H)+

Test Example 1: Comparison of Protection Reaction at C-Terminus Due to Difference in Silylating Agent

[0606] ##STR00092##

[0607] [Test Compounds]

[0608] As the silylating agent, trimethylsilyl chloride (TMS-Cl), t-butyldimethylsilyl chloride (TBS-Cl) and di-t-butylisobutylsilyltriflate (BIBS-OTf) were used.

[0609] As the N-protected amino acid, commercially available Boc-Phe-OH, Fmoc-Phe-OH and Cbz-Phe-OH were used.

[0610] [Test Method]

[0611] N-protected amino acid and imidazole (1.5 equivalents) were mixed with methylene chloride (20-fold by mass), the mixture was cooled to 0 C., a silylating agent (1.2 equivalents) was added dropwise thereto and the mixture was stirred at room temperature for 3 hours. The obtained reaction mixture was washed with an aqueous saturated ammonium chloride solution and water, the obtained organic layer was concentrated, and the presence or absence of formation of the objective material (crude material) was confirmed by .sup.1H-NMR and LC-MS. Further, a compound which was capable of carrying out was purified by silica gel column chromatography.

[0612] [Test Results]

[0613] When TMS-Cl was used, formation of the objective material could not be confirmed in either of the N-protected amino acids. In addition, when TBS-Cl was used, formation of the objective material could be confirmed as the crude material in any of the N-protected amino acids, but in the subsequent silica gel column chromatography, the objective material was decomposed. On the other hand, when BIBS-OTf was used, the objective material could be obtained with good yield in any of the N-protected amino acids.

TABLE-US-00001 TABLE 1 Silylating agent TMSCl TBSCl BIBSOTf Objective material BocPheOTMS BocPheOTBS BocPheOBIBS With or without None None Done purification Results No objective Objective material was Yield: 89% material obtained obtained as crude material but decomposed by silica gel column chromatography

TABLE-US-00002 TABLE 2 Silylating agent TMSCl TBSCl BIBSOTf Objective material CbzPheOTMS CbzPheOTBS CbzPheOBIBS With or without None None Done purification Results No objective Objective material was Yield: 91% material obtained obtained as crude material but decomposed by silica gel column chromatography

TABLE-US-00003 TABLE 3 Silylating agent TMSCl TBSCl BIBSOTf Objective material FmocPheOTMS FmocPheOTBS FmocPheOBIBS With or without None None Done purification Results No objective Objective material was Yield: 99% material obtained obtained as crude material but decomposed by silica gel column chromatography

[0614] Boc-Phe-OTBS

[0615] .sup.1H-NMR (CDCl.sub.3)

[0616] ppm: 0.25 (3H, s), 0.26 (3H, s), 0.91 (9H, s), 1.42 (9H, s), 3.03-3.17 (2H, m), 4.52-4.58 (1H, m), 4.98 (1H, d, J=8.1 Hz), 7.13-7.31 (10H, m)

[0617] MASS (ESI+) m/z; 380.22 (M+H)+

[0618] Boc-Phe-OBIBS

[0619] .sup.1H-NMR (CDCl.sub.3)

[0620] ppm: 0.86 (2H, d, J=6.6 Hz), 0.96 (3H, d, J=6.6 Hz), 0.97 (3H, d, J=6.6 Hz), 1.04 (9H, s), 1.05 (9H, s), 1.38 (9H, s), 1.94-2.07 (1H, m), 2.98 (1H, dd, J=7.4, 14.0 Hz), 3.22 (1H, dd, J=5.5, 14.0 Hz), 4.53-4.60 (1H, m), 4.93 (1H, d, J=8.5 Hz), 7.18-7.31 (10H, m)

[0621] MASS (ESI+) m/z; 464.31 (M+H)+

[0622] Cbz-Phe-OTBS

[0623] .sup.1H-NMR (CDCl.sub.3)

[0624] ppm: 0.25 (3H, s), 0.26 (3H, s), 0.90 (9H, s), 3.01-3.20 (2H, m), 4.59-4.66 (1H, m), 5.09 (2H, d, J=2.9 Hz), 5.22 (1H, d, J=8.1 Hz), 7.10-7.39 (10H, m)

[0625] MASS (ESI+) m/z; 414.3 (M+H)+

[0626] Cbz-Phe-OBIBS

[0627] .sup.1H-NMR (CDCl.sub.3)

[0628] ppm: 0.87 (2H, d, J=6.6 Hz), 0.96 (3H, d, J=6.6 Hz), 0.97 (3H, d, J=6.3 Hz), 1.04 (9H, s), 1.05 (9H, s), 1.94-2.01 (1H, m), 3.01 (1H, dd, J=7.4, 14.0 Hz), 3.25 (1H, dd, J=5.2, 14.0 Hz), 4.60-4.65 (1H, m), 5.06 (2H, d, J=2.9 Hz), 5.15 (1H, d, J=8.5 Hz), 7.15-7.37 (10H, m)

[0629] MASS (ESI+) m/z; 498.5 (M+H)+

[0630] Fmoc-Phe-OTBS

[0631] .sup.1H-NMR (CDCl.sub.3)

[0632] ppm: 0.27 (3H, s), 0.27 (3H, s), 0.92 (9H, s), 3.01-3.22 (2H, m), 4.21 (1H, t, J=7.0 Hz), 4.31 (1H, dd, J=7.0, 10.3 Hz), 4.44 (1H, dd, J=7.0, 10.3 Hz), 4.61-4.68 (1H, m), 5.27 (1H, d, J=8.1 Hz), 7.12 (2H, dd, J=1.8, 7.7 Hz), 7.24-7.33 (5H, m), 7.40 (2H, t, J=7.4 Hz), 7.57 (2H, dd, J=3.7, 7.4 Hz), 7.76 (2H, d, J=7.7 Hz)

[0633] MASS (ESI+) m/z; 502.3 (M+H)+

[0634] Fmoc-Phe-OBIBS

[0635] .sup.1H-NMR (CDCl.sub.3)

[0636] ppm: 0.87 (2H, d, J=6.6 Hz), 0.97 (3H, d, J=6.6 Hz), 0.98 (3H, d, J=6.6 Hz), 1.05 (9H, s), 1.06 (9H, s), 1.95-2.08 (1H, m), 3.04 (1H, dd, J=7.0, 14.0 Hz), 3.29 (1H, dd, J=5.5, 14.0 Hz), 4.18 (1H, t, J=7.0 Hz), 4.26 (1H, dd, J=7.4, 10.3 Hz), 4.39 (1H, dd, J=7.4, 10.3 Hz), 4.61-4.68 (1H, m), 5.23 (1H, d, J=8.1 Hz), 7.18-7.31 (7H, m), 7.39 (2H, t, J=7.4 Hz), 7.53 (2H, t, J=7.0 Hz), 7.75 (2H, d, J=7.0 Hz)

[0637] MASS (ESI+) m/z; 586.4 (M+H)+

Test Example 2: Comparison of Deprotection Reaction of Protective Group at N-Terminus Due to Difference in Silyl Protective Group

[0638] ##STR00093##

[0639] [Test Compounds]

[0640] The protected amino acids (Boc-Phe-OTBS, Boc-Phe-OBIBS, Cbz-Phe-OTBS, Cbz-Phe-OBIBS, Fmoc-Phe-OTBS and Fmoc-Phe-OBIBS) synthesized in Test Example 1 were used as the test compounds.

[0641] [Test Method 1: Deprotection Reaction of Boc Group]

[0642] Boc-Phe-OTBS and Boc-Phe-OBIBS were each mixed with methylene chloride (20-fold by mass), the mixture was cooled to 0 C., 15% by mass hydrogen chloride-1,4-dioxane (10-fold by mass) was added thereto and the mixture was stirred at room temperature for 5 to 7 hours. The obtained reaction mixture was diluted with chloroform, and washed with a saturated aqueous sodium carbonate solution and water. The obtained organic layer was concentrated, and the presence or absence of formation of the objective material was confirmed by .sup.1H-NMR and LC-MS.

[0643] [Test Results 1]

[0644] In the case of Boc-Phe-OTBS, formation of the objective material could not be confirmed. On the other hand, in Boc-Phe-OBIBS, the objective material could be obtained with good yield.

TABLE-US-00004 TABLE 4 Protected amino acid BocPheOTBS BocPheOBIBS Objective material HPheOTBS HPheOBIBS With or without None None purification Results No objective material Yield: 100% could be obtained

[0645] H-Phe-OBIBS

[0646] .sup.1H-NMR (CDCl.sub.3)

[0647] ppm: 0.89 (2H, d, J=7.7 Hz), 0.99 (6H, d, J=6.6 Hz), 1.07 (9H, s), 1.07 (9H, s), 1.98-2.11 (1H, m), 2.74 (1H, dd, J=9.2, 13.3 Hz), 3.24 (1H, dd, J=4.4, 13.6 Hz), 3.71 (1H, dd, J=4.4, 9.2 Hz), 7.19-7.34 (5H, m)

[0648] MASS (ESI+) m/z; 364.3 (M+H)+

[0649] [Test Method 2: Deprotection Reaction of Cbz Group]

[0650] Cbz-Phe-OTBS and Cbz-Phe-OBIBS were each mixed with 2,2,2-trifluoroethanol (20-fold by mass), 10% by mass PdC (0.2-fold by mass) was added thereto and the mixture was stirred under a hydrogen gas atmosphere at room temperature for 24 hours. The reaction mixture was filtered and the obtained filtrate was concentrated, and the presence or absence of formation of the objective material was confirmed by .sup.1H-NMR and LC-MS.

[0651] [Test Results 2]

[0652] In the case of Cbz-Phe-OTBS, formation of the objective material could not be confirmed. On the other hand, in Cbz-Phe-OBIBS, the objective material could be obtained with good yield.

TABLE-US-00005 TABLE 5 Protected amino acid CbzPheOTBS CbzPheOBIBS Objective material HPheOTBS HPheOBIBS With or without None None purification Results No objective material Yield: 100% could be obtained

[0653] Incidentally, .sup.1H-NMR and LC-MS of H-Phe-OBIBS in Test Results 2 were accorded with .sup.1H-NMR and LC-MS in Test Results 1.

[0654] [Test Method 3: Deprotection Reaction of Fmoc Group]

[0655] Fmoc-Phe-OTBS and Fmoc-Phe-OBIBS were each mixed with methylene chloride (20-fold by mass), the mixture was cooled to 0 C., diethylamine (15-fold by mass) was added thereto and the mixture was stirred at room temperature for 5 to 7 hours. The obtained reaction mixture was diluted with chloroform, and washed with an aqueous saturated ammonium chloride solution and water. The obtained organic layer was concentrated and purified by silica gel column chromatography, and the presence or absence of formation of the objective material was confirmed by .sup.1H-NMR and LC-MS.

[0656] [Test Results 3]

[0657] In the case of Fmoc-Phe-OTBS, formation of the objective material could not be confirmed. On the other hand, in Fmoc-Phe-OBIBS, the objective material could be obtained with good yield.

TABLE-US-00006 TABLE 6 Protected amino acid FmocPheOTBS FmocPheOBIBS Objective material HPheOTBS HPheOBIBS With or without purification None None Results No objective material Yield: 87% could be obtained

[0658] Incidentally, .sup.1H-NMR and LC-MS of H-Phe-OBIBS in Test Results 3 were accorded with .sup.1H-NMR and LC-MS in Test Results 1.

Test Example 3: Comparison of Condensing Step of Each N-Protected Amino Acid and H-Phe-OBIBS

[0659] ##STR00094##

[0660] [Test Compounds]

[0661] H-Phe-OBIBS synthesized in Test Example 2 and the N-protected amino acids (Boc-Phe-OH, Fmoc-Phe-OH and Cbz-Phe-OH) were used.

[0662] [Test Method]

[0663] H-Phe-OBIBS and each N-protected amino acid (1.2 equivalents) were mixed with methylene chloride (20-fold by mass), the mixture was cooled to 0 C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (1.2 equivalents) were added thereto and the mixture was stirred for 3 hours. The obtained reaction mixture was diluted with chloroform, and then, washed with an aqueous saturated sodium hydrogen carbonate solution, an aqueous saturated ammonium chloride solution and water in this order. The obtained organic layer was concentrated and purified by silica gel column chromatography, and the presence or absence of formation of the objective material was confirmed by .sup.1H-NMR and LC-MS.

[0664] [Test Results]

[0665] In each N-protected amino acid, the objective material could be obtained with good yield.

TABLE-US-00007 TABLE 7 N-Protected BocPheOH CbzPheOH FmocPheOH amino acid Objective BocPhePheOBIBS CbzPhePheOBIBS FmocPhePheOBIBS material With or without Done Done Done purification Results Yield: 93% Yield: 86% Yield: 91%

[0666] Boc-Phe-Phe-OBIBS

[0667] .sup.1H-NMR (CDCl.sub.3)

[0668] ppm: 0.85 (2H, d, J=6.6 Hz), 0.97 (6H, d, J=6.6 Hz), 1.03 (9H, s), 1.04 (9H, s), 1.39 (9H, s), 1.93-2.06 (1H, m), 2.96-3.09 (3H, m), 3.22 (1H, dd, J=5.5, 14.0 Hz), 4.28-4.34 (1H, m), 4.72-4.79 (1H, m), 4.86 (1H, brs), 6.34 (1H, d, d=8.5 Hz), 7.05-7.08 (2H, m), 7.14-7.29 (8H, m)

[0669] MASS (ESI+) m/z; 611.38 (M+H)+

[0670] Cbz-Phe-Phe-OBIBS

[0671] .sup.1H-NMR (CDCl.sub.3)

[0672] ppm: 0.86 (2H, d, J=6.6 Hz), 0.97 (6H, d, J=6.3 Hz), 1.04 (9H, s), 1.05 (9H, s), 1.94-2.07 (1H, m), 2.92-3.01 (3H, m), 3.23 (1H, dd, J=5.5, 14.0 Hz), 4.35-4.42 (1H, m), 4.72-4.79 (1H, m), 5.06 (1H, s), 5.14 (1H, d, d=7.4 Hz), 6.28 (1H, d, J=7.4 Hz), 7.03-7.38 (15H, m)

[0673] MASS (ESI+) m/z; 645.5 (M+H)+

[0674] Fmoc-Phe-Phe-OBIBS

[0675] .sup.1H-NMR (CDCl.sub.3)

[0676] ppm: 0.86 (2H, d, J=6.7 Hz), 0.97 (6H, d, J=6.4 Hz), 1.04 (9H, s), 1.05 (9H, s), 1.93-2.04 (1H, m), 2.92-3.05 (3H, m), 3.23 (1H, dd, J=5.5, 14.1 Hz), 4.17 (1H, t, J=7.0 Hz), 4.28 (1H, m), 4.38 (1H, m), 4.43 (dd, J=6.7, 10.4 Hz), 4.75 (1H, dd, J=7.0, 13.2 Hz), 5.15 (1H, d, J=8.0 Hz), 6.24 (1H, d, J=7.0 Hz), 7.01-7.04 (2H, m), 7.13-7.33 (10H, m), 7.40 (2H, t, J=7.7 Hz), 7.45-7.54 (2H, m), 7.77 (2H, d, J=7.7 Hz)

[0677] MASS (ESI+) m/z; 733.6 (M+H)+

Utilizable Field in Industry

[0678] According to the present invention, a method for producing a peptide with high efficiency can be provided.