Process for preparing ceftolozane from 7-aminocephalosporanic acid (7-ACA)

Abstract

The present invention relates to a highly convergent method for the synthesis and purification of ceftolozane and intermediates starting from 7-aminocephaiosporanic acid (7-ACA).

Claims

1. A method for preparing a compound of formula ##STR00084## wherein R.sub.6 is hydrogen or a negative charge, and A.sup. an anion, with the condition that n is zero when R.sub.6 is a negative charge, and n is one when R.sub.6 is hydrogen, comprising the steps of a) preparing a compound of formula ##STR00085## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently an amino protecting group or hydrogen with the condition that R.sub.4 is not hydrogen if R.sub.3 is hydrogen, or R.sub.1 and R.sub.2, and/or R.sub.3 and R.sub.4 are bound together by a cyclic amino protecting group, R.sub.5 is trialkylsilyl or hydrogen, R.sub.6 is trialkylsilyl, hydrogen or a negative charge, and A.sub.1.sup. is an anion, with the condition that n is zero when R.sub.6 is a negative charge, and n is one when R.sub.6 is trialkylsilyl or hydrogen, which comprises the steps of a-i) reacting a compound of formula ##STR00086## with a silylating agent, optionally in presence of a catalyst, and with iodotrialkylsilane, a-ii) providing a compound of formula ##STR00087## wherein R.sub.1-R.sub.4 are as defined above, and optionally reacting this compound of formula IV with a silylating agent, a-iii) reacting the products of steps a-i) and a-ii), a-iv) and optionally desilylating the product of step a-iii) to produce the compound of formula II b) preparing a compound of formula ##STR00088## wherein R.sub.1-R.sub.4 and R.sub.6 are as defined above, R.sub.7 is hydrogen or an amino protecting group, R.sub.10 is an ester protecting group, and A.sub.2.sup. is an anion, with the condition that n is zero when R.sub.6 is a negative charge, and n is one when R.sub.6 is hydrogen, which comprises the step of reacting the compound of formula II with a compound of formula ##STR00089## wherein R.sub.7 and R.sub.10 are as defined above, R.sub.8 is Cl or SR.sub.9, wherein R.sub.9 is C.sub.1-C.sub.6 straight or branched alkyl, C.sub.3-C.sub.6 cycloalkyl, or a substituted or unsubstituted mono- or bicyclic aryl or heteroaryl ring system of 5 to 12 atoms and where each monocyclic ring contains 0 to 3 hetero atoms, and each bicyclic ring contains 0 to 4 hetero atoms selected from N, O and S, and c) removing any protecting groups from the compound of formula V to produce a compound of formula I, d) if in the compound of formula I produced in step c) R.sub.6 is a negative charge and n is zero optionally treating the compound of formula I produced in step c) with an acid to produce a compound of formula I, wherein R.sub.6 is hydrogen and n is one, e) optionally exchanging the anion by a different anion in the compound of formula I produced in step d) or in the compound of formula I produced in step c) if R.sub.6 is hydrogen and n is one.

2. The method of claim 1, comprising the step a-ii) reacting a compound of formula ##STR00090## wherein R.sub.1-R.sub.4 are as defined in claim 1, with a silylating agent.

3. The method of claim 1, wherein step a-iii) is carried out in the presence of a metal catalyst.

4. The method of claim 1, wherein in each of the compounds of formulae II, IV, and V, at least one of R.sub.1 and R.sub.2 is triphenylmethyl, trialkylsilyl, tert-butyldimethylsilyl or triisopropylsilyl, or tert-butyldiphenylsilyl or R.sub.1 and R.sub.2 are both benzyl or both allyl, at least one of R.sub.3 and R.sub.4 is tert-butyloxycarbonyl, triphenylmethyl, benzoyloxycarbonyl (Cbz), allyloxycarbonyl (Aloc), 9-fluorenylmethoxycarbonyl (Fmoc), methoxycarbonyl, ethoxycarbonyl, 2-(trimethylsilyl)ethoxycarbonyl (Teoc), 2,2,2-trichlorethoxycarbonyl (Troc) or part of a triazinanone or trimethylsilyl or R.sub.3 and R.sub.4 are both benzyl, allyl, or (p-methoxybenzyl), R.sub.5 and R.sub.6 are trimethylsilyl, R.sub.7 is hydrogen, R.sub.8 is Cl or ##STR00091##

5. The method of claim 1, wherein steps a-i) and a-ii) are independently conducted in one or a combination of two or more solvents selected from the group consisting of N-methyl-2-pyrrolidone, 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H)-pyrimidinone, dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, dimethylformamide, dimethyl sulfoxide or methylene chloride.

6. The method of claim 1, wherein the compound of formula II is not isolated from the reaction mixture of step a) before it is reacted with the compound of formula VI in step b).

7. The method of claim 1, wherein one or more acids are used in step c) for removing any protecting groups from the compound of formula V to produce a compound of formula I, wherein R.sub.6 is hydrogen and n is one.

8. The method of claim 1, wherein R.sub.1 is triphenylmethyl and R.sub.2 is hydrogen and step c) comprises a step c1) wherein all triphenylmethyl groups are selectively removed from the compound of formula V ##STR00092## to produce a compound of formula VII ##STR00093## wherein R.sub.3, R.sub.4, R.sub.6, R.sub.7 and R.sub.10 are defined as R.sub.3, R.sub.4, R.sub.6, R.sub.7 and R.sub.10 in claim 1, respectively with the exception that R.sub.3, R.sub.4, R.sub.7 and R.sub.10 are not triphenylmethyl and if R.sub.3 and/or R.sub.4 and/or R.sub.7 and/or R.sub.10 are triphenylmethyl in the compound of formula V R.sub.3 and/or R.sub.4 and/or R.sub.7 and/or R.sub.10 are hydrogen in the compound of formula VII, respectively, and A.sub.3.sup. is an anion, with the condition that n is zero when R.sub.6 is a negative charge, and n is one when R.sub.6 is hydrogen.

9. The method of claim 8, wherein formic acid in ethanol is used in step c1) for selectively removing all triphenylmethyl groups, from the compound of formula V to form a compound of formula VII, wherein R.sub.6 is hydrogen, n is one and A.sub.3.sup. is formate.

10. The method of claim 8, wherein the reaction mixture of step c1) is subjected to an aqueous workup and insoluble precipitate is removed before any remaining protective groups of the compound of formula VII are removed in a step c2) to produce a compound of formula I.

11. The method of claim 1, wherein in step c) H.sub.2SO.sub.4 is used to produce a compound of formula I, wherein R.sub.6 is hydrogen, n is one and A.sup. is HSO.sub.4.sup. and a solvent is used, which is selected from one or a combination of two or more solvents of the group consisting of 2,2,2,-trifluoroethanol, methyl isobutyl ketone, 2-ethoxyethanol, acetic acid, methyl ethyl ketone, dimethylcarbonate and acetonitrile.

12. A method for preparing a compound of formula I as defined in claim 1 from a compound of formula V ##STR00094## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently an amino protecting group or hydrogen with the condition that R.sub.4 is not hydrogen if R.sub.3 is hydrogen, or R.sub.1 and R.sub.2, and/or R.sub.3 and R.sub.4 are bound together by a cyclic amino protecting group, R.sub.6 is hydrogen or a negative charge, and R.sub.7 is hydrogen or an amino protecting group, R.sub.10 is an ester protecting group, and A.sub.2.sup. is an anion, with the condition that n is zero when R.sub.6 is a negative charge, and n is one when R.sub.6 is hydrogen, or from a compound of formula VII ##STR00095## wherein R.sub.3, R.sub.4, R.sub.6, R.sub.7 and R.sub.10 are defined as R.sub.3, R.sub.4, R.sub.6, R.sub.7 and R.sub.10 in claim 1, respectively with the exception that R.sub.3, R.sub.4, R.sub.7 and R.sub.10 are not triphenylmethyl and if R.sub.3 and/or R.sub.4 and/or R.sub.7 and/or R.sub.10 are triphenylmethyl in the compound of formula V R.sub.3 and/or R.sub.4 and/or R.sub.7 and/or R.sub.10 are hydrogen in the compound of formula VII, respectively, and A.sub.3.sup. is an anion, with the condition that n is zero when R.sub.6 is a negative charge, and n is one when R.sub.6 is hydrogen.

13. A method for preparing a compound of formula VII as defined in claim 8 from a compound of formula V ##STR00096## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently an amino protecting group or hydrogen with the condition that R.sub.4 is not hydrogen if R.sub.3 is hydrogen, or R.sub.1 and R.sub.2, and/or R.sub.3 and R.sub.4 are bound together by a cyclic amino protecting group, R.sub.6 is hydrogen or a negative charge, and R.sub.7 is hydrogen or an amino protecting group, R.sub.10 is an ester protecting group, and A.sub.2.sup. is an anion, with the condition that n is zero when R.sub.6 is a negative charge, and n is one when R.sub.6 is hydrogen, comprising a step c1) as defined in claim 8.

14. The method of claim 10, wherein in step c2) H.sub.2SO.sub.4 is used to produce a compound of formula I, wherein R.sub.6 is hydrogen, n is one and A.sup. is HSO.sub.4.sup. and a solvent is used, which is selected from one or a combination of two or more solvents of the group consisting of 2,2,2,-trifluoroethanol, methyl isobutyl ketone, 2-ethoxyethanol, acetic acid, methyl ethyl ketone, dimethylcarbonate and acetonitrile.

Description

EXAMPLE 1

2-(((6R,7R)-7-((Z)-2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(((1-(tert-butoxy)-2-methyl-1-oxopropan-2-yl)oxy)imino)acetamido)-2-carboxy-8-oxo-5-thia-1-azabicyclo[4.2.0]-oct-2-en-3-yl)methyl)-4-(3-(2((tert-butoxycarbonyl)amino)ethyl)ureido)-1-methyl-5-(trityl-amino)-1H-pyrazol-2-ium 2,2,2-trifluoroacetate

(1) 7-ACA (30.0 g, 110.8 mmol) was dissolved in 570 mL CH.sub.2Cl.sub.2 and heated to 60 C. HMDS (2-3 mL) and TMJS (100 L) were added and the solution was purged with N.sub.2. Within 20 min the remaining HMDS (68.39 mL, 52.35 g, 3 eq) was added dropwise and the reaction mixture was further refluxed for 4 hours while purging the solution with N.sub.2. Then the solution was cooled to RT and evaporated to dryness. The residual solid was dissolved with 120 mL CH.sub.2Cl.sub.2 and cooled to 5 C. TMJS (26.46 g, 132.22 mmol, 1.2 eq) was added dropwise over 20 min and the reaction mixture was stirred at 5 C. over night (Solution A).

(2) ##STR00076##

(3) tert-Butyl (2-(3-(1-methyl-5-(tritylamino)-1H-pyrazol-4-yl)ureido)ethyl)carbamate (T-BAMPU, 71.5 g, 132.22 mmol, 1.2 eq) was dissolved in 240 mL dry NMP at 45-50 C. Then the solution was cooled to RT and proton Sponge (23.61 g, 110.18 mmoL, 1.0 eq) and BSA (26.90 g, 132.22 mmoL, 1.2 eq) were added. After stirring the reaction mixture for 1 hour, solution A (see above) was added dropwise within 10 min. The remaining solution was stirred for 22 hours at room temperature. After cooling the reaction mixture to 0 C., (Z)-tert-butyl 2-(((1-(5-amino-1,2,4-thiadiazol-3-yl)-2-chloro-2-oxoethylidene)amino)oxy)-2-methy propanoate (BATDPO-CL, 40.4 g, 115.69 mmol, 1.05 eq) was added in small portions, whereby the reaction temperature remained below 5 C. The solution was stirred at 0-5 C. for 4 hours and subsequently filtered to remove the protonated proton Sponge. The reaction mixture was quenched with an aqueous NaHCO.sub.3 solution (5%, 500 mL) and the aqueous phase was extracted with CH.sub.2Cl.sub.2 (2500 mL). The combined organic phases were subsequently washed with half saturated NH.sub.4Cl solution (500 mL), then H.sub.2O (500 mL) and dried over Na.sub.2SO.sub.4. The remaining solution was concentrated under reduced pressure to 400 mL and then was added slowly to a stirred aqueous NaTFA solution (30 g/3 L, pH=8) under ice cooling. The orange precipitate was filtered off, washed with cold water (500 mL) and cyclohexane (200 mL). The residual solid (290 g, 10 w/w % BTBOC-CTOL=29 g BTBOC-CTOL) was stored at 20 C. ESI-MS: m/z 1065.4 (M+)

EXAMPLE 2

5-amino-2-(((6R,7R)-7-((Z)-2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(((1-(tert-butoxy)-2-methyl-1-oxopropan-2-yl)oxy)imino)acetamido)-2-carboxy-8-oxo-5-thia-1-aza-bicyclo[4.2.0]oct-2-en-3-yl)methyl)-4-(3-(2-((tert-butoxycarbonyl)amino)ethyl)ureido)-1-methyl-1H-pyrazol-2-ium formate

(4) ##STR00077##

(5) Crude TBOC-CTOL (10 w/w %) from example 1 (70 g) was dissolved in dry ethanol (150 mL) and conc. formic acid (150 mL) and stirred at 15 C. over night. Then the reaction mixture was poured slowly into ice cold water (2.5 L), further stirred for 2 hours and celite was added. The precipitate was filtered off, washed with water and the remaining aqueous solution was loaded on a RP-silica column (solid phase extraction). The column was washed with water and then BBOC-CTOL was eluted with ethanol (100 mL). The resulting solution was azeotropically dried with toluene and subsequently with Na.sub.2SO.sub.4 to remove traces of water. Then pentane was added slowly to the mixture, resulting in the formation of a white solid (BBOC-CTOL, Yield: 4.38 g). Reslurrying the solid for 2 days in acetonitrile yielded crystalline BBOC-CTOL. H-NMR (400 MHz, D2): 8.10 (s, 1H, formate), 7.94 (s, 1H, CH), 5.86 (d, J=4.9 Hz, 1H, CH), 5.28 (d, J=15.4 Hz, 1H, CH.sub.2), 5.12 (d, J=4.9 Hz, 1H, CH), 5.00 (d, J=14.7 Hz, 1H, CH.sub.2), 3.75 (s, 3H, CH3), 3.36 (d, J=17.6 Hz, 1H, CH.sub.2), 3.27-3.10 (m, 5H, CH.sub.2), 1.57 (s, 3H, CH.sub.3), 1.56 (s, 3H, CH.sub.3), 1.46 (s, 9H, CH.sub.3), 1.44 (s, 9H, CH.sub.3). ESI-MS: m/z 823.3 (M+)

EXAMPLE 3

5-amino-2-(((6R,7R)-7-((Z)-2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(((2-carboxypropan-2-yl)oxy)imino)acetamido)-2-carboxy-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-3-yl)methyl)-4-(3-(2-aminoethyl)ureido)-1-methyl-1H-pyrazol-2-ium hydrogensulfate

(6) ##STR00078##

(7) BBOC-CTOL (21.5 g, 55 w/w %) was dissolved in 300 mL trifluoroethanol and the mixture was cooled to 0 C. using an ice-bath. A solution of conc. H.sub.2SO.sub.4 (10 ml) in 50 mL trifluoroethanol was added and the reaction was stirred at rt for 2 hours. A white solid started to precipitate, which was filtered off, the residue was washed with trifluoroethanol and suction dried over N.sub.2. The resulting solid was dissolved in water and filtered over a pad of LiChroprep RP-18, eluting with a gradient from 1.5 to 3% ethanol in water. The resulting solution was concentrated under reduced pressure to 500 ml and isopropanol (2 L) was added slowly to the solution, allowing the precipitation of ceftolozane sulfate (Yield: 5.1 g). .sup.1H-NMR (400 MHz, D.sub.2O): 7.89 (s, 1H, CH), 5.85 (d, J=4.8 Hz, 1H, CH), 5.23 (d, J=4.8 Hz, 1H, CH), 5.19 (d, J=14.7 Hz, 1H, CH.sub.2), 4.96 (d, J=14.7 Hz, 1H, CH.sub.2), 3.70 (s, 3H, CH.sub.3), 3.47 (t, J=5.8 Hz, 1H, CH.sub.2), 3.45 (d, J=17.5 Hz, 1H, CH.sub.2), 3.21 (d, J=17.8 Hz, 1H, CH.sub.2), 3.13 (t, J=5.7 Hz, 1H, CH.sub.2), 1.52 (s, 3H, CH.sub.3), 1.51 (s, 3H, CH.sub.3); ESI-MS: m/z 667.2 (M.sup.+)

EXAMPLE 4

(8) For global deprotection different conditions were tested:

(9) ##STR00079##

(10) TABLE-US-00002 experiment acid solvent(s) Product formed appearance 1 H2SO4 (6 eq.) HOAc x sticky precipitate 2 H2SO4 (6 eq.) Acetonitrile (x) sticky suspension 3 H2SO4 (6 eq.) MeOH solution 4 H2SO4 (6 eq.) EtOH sticky precipitate 5 H2SO4 (6 eq.) EtOAc x suspension 6 H2SO4 (6 eq.) Diethylcarbonate sticky suspension 7 H2SO4 (6 eq.) DMAc solution 8 H2SO4 (6 eq.) 2-Butanone x suspension 9 H2SO4 (6 eq.) MIBK x suspension 10 H2SO4 (6 eq.) CH2Cl2 sticky suspension 11 H2SO4 (6 eq.) Diethylcarbonate (x) sticky precipitate 12 H2SO4 (6 eq.) 2,2,2-Trifluorethanol x suspension 13 H2SO4 (6 eq.) Isopropanol (ISO) 14 H2SO4 (6 eq.) ISO/HOAc (3/1) sticky suspension 15 H2SO4 (12 eq.) MIBK/H2O x biphasic mixture 17 H2SO4 (6 eq.) EtOAc/HOAc (1/1) x sticky suspension 18 H2SO4 (6 eq.) MIBK x suspension 19 H2SO4 (6 eq.) MIBK (more diluted) x suspension 20 H2SO4 (6 eq.) EtOAc/HOAc (1/1) x suspension 21 H2SO4 (6 eq.) EtOAc (double dil.) x suspension 22 H2SO4 (6 eq.) EtOAc/HOAc (6/1) x suspension 23 H2SO4 (18 eq.) MIBK (x) decomposition 24 H2SO4 (6 eq.) MIBK (x) incomplete conv. 25 TFA Anisole/CH2Cl2 x suspension The best yield (80%) and fastest reaction was obtained with H.sub.2SO.sub.4 in trifluoroethanol (example 12). The yield of the reaction with TFA in anisole/CH.sub.2Cl.sub.2 was 70%.

EXAMPLE 5

(Z)-tert-butyl 2-(((1-(5-amino-1,2,4-thiadiazol-3-yl)-2-chloro-2-oxoethylidene)-amino)oxy)-2-methylpropanoate

(11) ##STR00080##

(12) BATDPO ((Z)-2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(((1-(tert-butoxy)-2-methyl-1-oxopropan-2-yl)oxy)imino)acetic acid) (80 g, 0.242 mol, 1 eq) was suspended in 1080 mL CH.sub.2Cl.sub.2 and was cooled to 12 C. DMF (932 L, 0.05 eq) and oxalyl chloride (24.92 mL, 0.290 mmol, 1.2 eq) was added within 5 min. The reaction mixture was poured into 6 L diisopropylether after stirring for 75 min. The suspension was further stirred for 3 hours at 0 C., filtered and dried under vacuum to yield 84.4 g of BATDPO-Cl. ((Z)-tert-butyl 2-(((1-(5-amino-1,2,4-thiadiazol-3-yl)-2-chloro-2-oxoethylidene)amino)oxy)-2-methylpropanoate). H-NMR (400 MHz, THF-D8): 7.59 (bs, 2H, NH.sub.2), 1.52 (s, 6H, CH.sub.3), 1.42 (s, 9H, CH.sub.3)

EXAMPLE 6

(Z)-tert-butyl 2-(((1-(5-amino-1,2,4-thiadiazol-3-YL)-2-(benzo[D]thiazol-2-ylthio)-2-oxoethylidene)amino)oxy)-2-methylpropanoate

(13) ##STR00081##

(14) BATDPO ((Z)-2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(((1-(tert-butoxy)-2-methy-1-oxopropan-2-yl)oxy)imino)acetic acid) (30 g, 90.8 mmol, 1 eq), 2,2-dithiobis(benzothiazole) (36.2 g, 108.9 mmol, 1.2 eq) and triphenylphosphine (29.7 g, 113.2 mmol, 1.2 eq) was suspended in 450 mL CH.sub.2Cl.sub.2 and cooled to 0 C. Triethylamine (15.15 mL, 109.3 mmol, 1.2 eq) was added within 2 min. The reaction was stirred for 30 min at room temperature, cooled to 0 C. using an ice-bath and the crystalline solid was filtered off after 60 min to yield 30.0 g (Z)-tert-butyl 2-(((1-(5-amino-1,2,4-thiadiazol-3-yl)-2-(benzo[d]thiazol-2-ylthio)-2-oxoethylidene)amino)-oxy)-2-methylpropanoate. .sup.1H-NMR (400 MHz, THF-D8): 8.07 (d, J=7.9 Hz, 1H, CH) 8.02 (d, J=8.1 Hz, 1H, CH) 7.60 (bs, 2H, NH.sub.2), 7.53 (pseudo dt, J=7.6, 1.2 Hz, 1H, CH), 7.47 (pseudo dt, J=7.7, 1.0 Hz, 1H, CH), 1.57 (s, 6H, CH.sub.3), 1.49 (s, 9H, CH.sub.3)

EXAMPLE 7

5-amino-2-(((6R,7R)-7-((Z)-2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(((1-(tert-butoxy)-2-methyl-1-oxopropan-2-yl)oxy)imino)acetamido)-2-carboxy-8-oxo-5-thia-aza-bicyclo[4.2.0]oct-2-en-3-yl)methy)-4-(3(2-((tert-butoxycarbonyl)amino)ethyl)ureido)-1-methyl-1H-pyrazol-2-ium acetate

(15) ##STR00082##

(16) 7-ACA (20.0 g, 73.45 mmol) was dissolved in 380 mL CH.sub.2Cl.sub.2 and heated to 60 C. HMDS (2 mL) and TMJS (20 L) were added and the solution was purged with N.sub.2. Within 20 min the remaining HMDS ( 45.6 mL, 35.6 g, 220.36 mmol, 3 eq) was added dropwise and the reaction mixture was further refluxed for 6 hours while purging the solution with N.sub.2. Then the solution was cooled to RT and evaporated to dryness. The residual solid was dissolved with 80 mL CH.sub.2Cl.sub.2 (c=0.5 mmol/g) (Solution A).

(17) Solution A (5 g, 2.50 mmol, bissilylated 7-ACA) cooled to 5 C. and TMJS (600 mg, 3 mmol, 1.2 eq) was added slowly. The reaction mixture was stirred at 50 C. overnight (Solution B). Tert-butyl (2-(3-(5-amino-1-methy-1H-pyrazol-4-yl)ureido)ethyl)carbamate (BAMPU) (895 mg, 3.0 mmol, 1.2 eq) was dissolved in 2.5 mL dry NMP and proton Sponge (536 mg, 2.5 mmoL, 1.0 eq) and BSA (1.36 mL, 1.13 g, 5.55 mmoL, 2.2 eq) were added. After stirring the reaction mixture for 2 hour, solution B (see above) was added slowly. The remaining solution was stirred for 22 hours at room temperature. After cooling the reaction mixture to 0 C., proton Sponge (589 mg, 2.75 mmoL, 1.1 eq) and BATDPO-CL (916 mg, 2.63 mmol, 1.05 eq) was added, whereby the reaction temperature remained below 5 C. The solution was stirred at 0-5 C. for 2 hours and subsequently filtered to remove the protonated proton Sponge. The reaction mixture was quenched with an aqueous NaHCO.sub.3 solution (5%, 10 mL) and the aqueous phase was extracted with CH.sub.2Cl.sub.2 (220 mL). The combined organic phases were subsequently washed twice with half saturated NH.sub.4Cl solution (10 mL), then H.sub.2O (10 mL) and dried over Na.sub.2SO.sub.4. The remaining solution was concentrated under reduced pressure to 30 mL and precipitate was formed after the addition of cyclohexane (100 mL). The residual solid was further purified by using a RP-HPLC (Gradient elution with CH.sub.3COONH.sub.4/CH.sub.3CN, pH=7) to yield 110 mg BBOC-CTOL.

(18) .sup.1H-NMR (400 MHz, D20): 7.94 (s, 1H, CH), 5.86 (d, J=4.9 Hz, 1H, CH), 5.28 (d, J=15.4 Hz, 1H, CH.sub.2), 5.12 (d, J=4.9 Hz, 1H, CH), 5.00 (d, J=14.7 Hz, 1H, CH.sub.2), 3.75 (s, 3H, CH3), 3.36 (d, J=17.6 Hz, 1H, CH.sub.2), 3.27-3.10 (m, 5H, CH.sub.2), 1.96 (s, 3H, acetate) 1.57 (s, 3H, CH.sub.3), 1.56 (s, 3H, CH.sub.3), 1.46 (s, 9H, CH.sub.3), 1.44 (s, 9H, CH.sub.3); ES-MS: m/z 823.3 (M+)

EXAMPLE 8

X-Ray Powder Diffraction Spectrum of BBOC-CTOL

(19) A sample of the crystalline BBOC-CTOL obtained in Example 2 was submitted to X-Ray powder diffraction (XRD), using a PANalytical X'Pert.sup.3 X-ray diffractometer with the following measurement configuration:

(20) TABLE-US-00003 Measurement Temperature [ C.] 25.00 Anode Material Cu K-Alpha1 [] 1.54060 K-Alpha2 [] 1.54443 K-Beta [] 1.39225 K-A2/K-A1 Ratio 0.50000 Generator Settings 40 mA, 45 kV.

(21) The following Table 1 shows the peak list of the XRD spectrum of BBOC-CTOL obtained in Example 2.

(22) TABLE-US-00004 TABLE 1 Pos. [2Th.] 0.2 Rel. Int. [%] 4.9 100 6.7 40 7.2 20 7.6 14 8.0 17 9.3 11 10.1 9 11.8 11 12.9 61 13.4 29 15.1 21

COMPARATIVE EXAMPLE

(23) WO 2014/152763 was repeated:

(24) ##STR00083##

(25) The yield for the 7-side chain coupling was considerably lower compared to what is indicated in WO 2014/152763. The yield for the global deprotection step (not indicated in WO 2014/152763) was very low (15%).