Method for obtaining novel derivatives of naphthalene for the in vivo diagnosis of alzheimer's disease

Abstract

This invention relates to a chemistry branch, particularly to the field of compounds' organic synthesis that belongs to the aromatic bicyclic or naphthalene category, used in the detection of amyloid sheets. These new naphthalene derivatives have a general formula: Wherein R represents mutually independent groups. In I: R.sub.1:-alkylenyl-C(O)NH-alkylenyl-R.sub.3, -alkylenyl-C(O)O—R.sub.4, R.sub.3:—COOH, —OH, —SH, —NH.sub.2, -alkyl-NH-alkyl-N-dithiocarbamate alkaline earth metal salts, R.sub.4: H, succinimidyl group, R.sub.2: —H,-alkyl. In II: R.sub.1: -alkyl, -alkylenyl-halide-alkylenyl-hydroxyl-alkylenyl-O-aryl, —O-alkylsulfonate alkylenyl, R.sub.2: -halide-alkylenyl-O-aryl, -alkylenyl-O-alkylsulfonate, -alkylenyl-halide-, —CH(O), —HC═C(CN).sub.2, —HC═CHNO.sub.2, -alkylenyl-NH.sub.2, -alkylenyl-NH-alkyl, -alkylenyl-alkyl-N-dithiocarbamate alkaline salts. The terms “alkyl” and “alkylenyl” refer to linear or branched aliphatic chains, preferably from 1 to 4 carbon atoms and the term halide to fluorine, bromine or iodine. These compounds are neutral, lipophilic and have low molecular weight and therefore they cross the blood brain barrier and attach to the amyloid sheets. The present invention provides procedures for obtaining naphthalene derivatives with good yields, which can be practical, economical and adapted to a larger-scale manufacturing. We are unaware whether the compounds presented in this invention have been previously reported.

Claims

1. An amyloid binding compound, said compound comprises structure I; ##STR00001## wherein; R.sub.1 is -alkylenyl-C(O)NH-alkylenyl-R.sub.3, or -alkylenyl-C(O)O—R.sub.4, R.sub.3 is —COOH, —OH, —SH, —NH.sub.2, —NH-alkyl or —N(-alkyl)-dithiocarbamate alkaline earth metal salts, R.sub.4 is a succinimidyl group, and R.sub.2 is H or alkyl, and wherein at least one or more of the oxygen or carbon atoms are substituted by a corresponding radioactive isotope or at least one of the hydrogen atoms of aromatic ring is substituted by halogen; wherein the compound has a partition coefficient LogP value of less than 1.6 so as to readily pass the blood brain barrier and selectively bind to amyloid sheets in a mammalian brain; whereby the amyloid binding compound is readily displayable in the mammalian brain.

2. The amyloid binding compound of claim 1, wherein the alkylenyl in R.sub.1 is selected from the group consisting of ethylene (—CH.sub.2CH.sub.2—) and butylenyl (—CH.sub.2CH.sub.2CH.sub.2CH.sub.2—); and the alkyl in R.sub.2 is selected from the group consisting of methyl, ethyl, n-propyl, iso-propyl, n-butyl and iso-butyl.

3. The amyloid binding compound of claim 1, wherein R.sub.1 is —(CH.sub.2).sub.nCONH(CH.sub.2).sub.m—R.sub.3 (n=2, 3 or 4 and m=2, 3, 4, 5 or 6), R.sub.3 is —COOH; and wherein R.sub.2 is —H or -alkyl.

4. The amyloid binding compound of claim 1, wherein R.sub.1 is —(CH.sub.2).sub.nCONH(CH.sub.2)m-R.sub.3 (n=2, 3 or 4 and m=2, 3, 4, 5 or 6), R.sub.3 is —NH.sub.2, —NHCH.sub.3 or —NHC.sub.2H.sub.5 and R.sub.2 is —H or -alkyl.

5. The amyloid binding compound of claim 1, wherein R.sub.1 is —(CH.sub.2).sub.nCONH(CH.sub.2).sub.m—R.sub.3(n=2, 3 or 4 and m=2, 3, 4, 5 or 6), R.sub.3 is —NR.sub.5R.sub.6, R.sub.5 is —CH.sub.3 or —C.sub.2H.sub.5, R.sub.6 is C(S)SW, W is Na.sup.+, K.sup.+ or Cs.sup.+ and R.sub.2 is —H or -alkyl.

6. The amyloid binding compound of claim 1, wherein R.sub.1 is —(CH.sub.2).sub.nCONH(CH.sub.2)m-R.sub.3 (n=2, 3 or 4 and m=2, 3, 4, 5 or 6), R.sub.3 is —OH and R.sub.2 is —H or -alkyl.

7. The amyloid binding compound of claim 1, wherein R.sub.1 is —(CH.sub.2).sub.nCONH(CH.sub.2).sub.m—R.sub.3 (n=2, 3 or 4 and m=2, 3, 4, 5 or 6), R.sub.3 is —SH and R.sub.2 is —H or -alkyl.

8. The amyloid binding compound of claim 1, wherein R.sub.1 is —(CH.sub.2).sub.nC(O)O—R.sub.4 (n=2, 3 or 4), R.sub.4 is a succinimidyl group and R.sub.2 is —H or -alkyl.

9. The amyloid binding compound of claim 1, wherein R.sub.1 is -alkylenyl-C(O)NH-alkylenyl-R.sub.3, and R.sub.3 is selected from the group consisting of —COOH, —OH, —SH, —NH.sub.2, —NH-alkyl and —N(-alkyl) -dithiocarbamate alkaline earth metal salts, in which at least one of the hydrogen atoms of aromatic ring is replaced by a radioactive halogen atom selected from the group consisting of .sup.123I, .sup.131I and .sup.18F.

10. The amyloid binding compound of claim 1, wherein R.sub.1 is -alkylenyl-C(O)NH-alkylenyl-R.sub.3, and R.sub.3 is selected from the group consisting of —COOH, —OH, —SH, —NH.sub.2, —NH-alkyl and —N(-alkyl) -dithiocarbamate alkaline earth metal salts, which is complexed with .sup.99mTc—, and a chelating ligand, wherein the chelating ligand is selected from the group consisting of 2,2′-oxydiethanethiol and N.sup.1-(2-aminoethyl)-1,2-ethanediamine.

11. The amyloid binding compound of claim 1, wherein at least one of the oxygen or carbon atoms are substituted by a corresponding radioactive isotope selected from the group consisting of .sup.11C and .sup.15O.

12. The amyloid binding compound of claim 1, wherein R.sub.1 is -alkylenyl-C(O)NH—alkylenyl-R.sub.3, and R.sub.3 is selected from the group consisting of —COON, —OH, —SH, —NH.sub.2, —NH-alkyl and —N(-alkyl)-dithiocarbamate alkaline earth metal salts, in which at least one of the hydrogen atoms of aromatic ring is replaced by a fluorine atom.

13. The amyloid binding compound of claim 9, wherein the amyloid binding compound is readily displayable in the mammalian brain by single photon emission computed tomography (SPECT) or positron emission tomography (PET) techniques.

14. The amyloid binding compound of claim 11, wherein the amyloid binding compound is readily displayable in the mammalian brain by positron emission tomography (PET) technique.

15. The amyloid binding compound of claim 12, wherein the amyloid binding compound is readily displayable in the mammalian brain by magnetic resonance imaging (MRI) technique.

16. The amyloid binding compound of claim 10, wherein the amyloid binding compound is readily displayable in the mammalian brain by single photon emission computed tomography (SPECT) technique.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows the general procedure for synthesis of derivatives 1-naphthyl derivatives with structure I, which includes the most relevant reaction conditions (a: succinic anhydride, NMM; b: succinic anhydride, c, c*: ethylenediamine or 1,4-butylenediamine d: NHS, DCC, e: 6-aminocaproic acid or β-alanine, f: a) CH.sub.3I, base, b) CS.sub.2, CsOH; g: Iodogeno in CHCl.sub.3 (.sup.131I).

(2) FIG. 2 shows the general procedure of synthesis of 2,6-naphthyl derivatives with structure II, which includes the most significant reaction conditions (a: Br.sub.2, Sn, glacial acetic acid; b: dimethylsulfate, base, acetone; c,: Mg, THF, Ar, d: 1,3-propanediol di-p-tosylate (PrDiTs) Li.sub.2CuCl.sub.4, THF, Ar; e: 1-butyl-3-methylimidazolium tetrafluoroborate, CsF, CH.sub.3CN).

(3) FIG. 3 shows the distribution of the N1-(2-aminoethyl)-N4-(1-naphthyl) succinimide (6) compound labeled with .sup.131I in rats, after its intravenous injection. The arrow indicates the detection of the compound in the region of interest (maximum uptake at about 3 min.).

(4) The obtaining procedures of naphthalene derivatives showed in the present invention are further illustrated by the following examples, which should not be regarded in any way, as constrain of the present invention. The compounds obtained were also appropriately characterized by spectroscopic techniques such as IR, .sup.1H and .sup.13C NMR and Mass.

DESCRIPTION OF THE EMBODIMENTS

EXAMPLE 1

1-(1-naphthyl)-2,5-pyrrolidinedione (1)

(5) 1-naphthylamine (5 g, 34.96 mmol) was dissolved in 50 mL of anhydrous 1,4-dioxane. Succinic anhydride (6.99 g, 69.92 mmol) and N-methylmorpholine (NMM, 7.6 mL, d=0.92 g/mL, 69.92 mmol) were added. The reaction mixture was heated at reflux for 5 hours. Once the reaction is completed (TLC), the solvent is removed by rotoevaporation. The solid residue is re-dissolved and re-crystallized from ethanol to obtain 5.2 g of compound 1 (Yield: 66%). Mp.: 153.5-154.5° C. (Lit: 153° C.). ESI-MS (m/z)=226 (M+1).sup.+.

EXAMPLE 2

4-(1-naphthylamino)-4-oxobutanoic acid (2)

(6) 1-naphthylamine (10 g, 69.84 mmol) and succinic anhydride (13.96 g, 140 mmol) were dissolved in 100 mL of anhydrous 1,4-dioxane. The reaction mixture was refluxed for 2 h and later, cooled to precipitate a violet solid which was filtered and washed with 1,4-dioxane. Recrystallization from ethanol gave 15.82 g of white solid. Yield: 93%. Mp.: 167-169° C. ESI-MS (m/z)=244 (M.+1).sup.+.

EXAMPLE 3

4-(1-naphthylamino)-4-oxobutanoic acid, N-hydroxysuccinimide ester (3)

(7) Compound 2 (2 g, 8.23 mmol), N-hydroxysuccinimide (NHS) (1.42 g, 12.34 mmol) and dicyclohexylcarbodiimide (DCC) (2.54 g, 12.33 mmol) were dissolved in 32 mL of anhydrous 1,4-dioxane. The reaction mixture was refluxed for 3 h. and then cooled at room temperature in order to remove the dicyclohexylurea (DCU) formed. The filtrate was rotoevaporated and cooled to separate by filtration a white solid that was washed with plenty of water and diethyl ether, and air-dried to obtain 2.29 g of product. Yield: 87%, Mp.: 168-171° C. ESI-MS (m/z)=341 (M.+1).sup.+.

EXAMPLE 4

N-[4-(1-naphthylamino)-4-oxobutanoyl]-β-alanine (4)

(8) Compound 2 (500 mg, 2.06 mmol) was dissolved in 13 mL of anhydrous 1,4-dioxane, and to this solution was added NHS (283 mg, 2.46 mmol) and DCC (507 mg, 2.46 mmol). The reaction mixture was refluxed for 3 h. and then cooled at room temperature in order to remove the dicyclohexylurea (DCU) formed. Then, β-alanine (248 mg, 2.78 mmol was added and the mixture was heated for 20 h. at 60° C. The solution was rotoevaporated to dryness and the crude product was purified by column chromatography with chloroform as mobile phase. 230 mg of a white solid was obtained. Yield: 40%. Mp.: 180.5-181.8° C. ESI-MS (m/z)=316 (M.+1).sup.+.

EXAMPLE 5

6-{[4-(1-naphthylamino)-4-oxobutanoyl]amino}hexanoic acid (5)

(9) 2 (1 g, 4.4 mmol), DCC (0.9 g, 4.4 mmol), 6-aminocaproic acid (0.6 g, 7.6 mmol) and triethylamine (0.6 mL, 4.3 mmol) in 40 mL of DMF were refluxed for 6 hours. Then, the mixture reaction was rotoevaporated to dryness and the crude product was recrystallized from ethanol. The solid thus obtained was dried over P.sub.2O.sub.5 to yield 0.28 g of 5. Yield: 18%. Mp.: 229-231° C. ESI-MS (m/z)=344 (M.+1).sup.+.

EXAMPLE 6

N1-(2-aminoethyl)-N4-(1-naphthyl) succinimide (6)

(10) Method A (One Pot): 2 (500 mg, 2.06 mmol) and NHS (283 mg, 2.46 mmol) were dissolved in 5 mL of anhydrous under dry N.sub.2 atmosphere. Next, a solution of DCC (507 mg, 2.46 mmol) in 8 mL of anhydrous 1,4-dioxane were added dropwise through a pressure equalizing dropping funnel. The reaction mixture was refluxed for 2 h. and then cooled at room temperature in order to remove the dicyclohexylurea (DCU) formed. A solution of ethylenediamine (0.18 mL, 2.7 mmol) in 1 mL of 1,4-dioxane was added. The reaction mixture was stirred at room temperature for 30 min. and then cooled to precipitate a white solid that was filtered, washed with 1,4-dioxane and acetone, and air-dried to yield 584 mg of the product (98%). Recrystallization from ether yielded 85% of pure 6. Mp.: 128.9-130.5° C.

(11) Method B: Compound 1 (2.58 g, 11.47 mmol) and ethylenediamine (7.66 mL, 11.4 mmol) in 30 ml of 1,4-dioxane were refluxed for 2 h. and then cooled at room temperature. 15 mL of diethyl ether was added to precipitate a white solid that was filtered and washed with diethyl ether to obtain 3.27 g of product. Recrystallization from acetone yielded 63% of pure 6. Mp.: 128.9-130.5° C. ESI-MS (m/z)=287 (M.+1).sup.+.

EXAMPLE 7

N1-(4-aminobutyl)-N4-(1-naphthyl) succinamic (7)

(12) Method A: Compound 2 (2.12 g, 8.72 mmol), NHS (1.42 g, 12.34 mmol) and DCC (2.54 g, 12.33 mmol) in 30 mL of anhydrous 1,4-dioxane were refluxed for 3 h. and then cooled at room temperature to remove the DCU formed. Butylenediamine (2.6 mL (26.14 mmol) was slowly dropped and the mixture reaction was stirred for 30 min. at room temperature. The mixture was rotoevaporated to dryness and the crude product re-dissolved in 10 ml of CHCl.sub.3 was washed with water (3×5 mL). Next, the organic phase was dried with anhydrous Na.sub.2SO.sub.4 and rotoevaporated to dryness. Diethyl ether (10 mL) was added to precipitate in cold a white solid. Yield: 72%. Mp.: 142.2-150.8° C.

(13) Method B

(14) Compound 1 (1.832 g, 8.1 mmol), triethylamine (1.94 mL, 14 mmol) and 1,4-butylenediamine (1.66 mL, 16.6 mmol) in 30 mL of DMF were refluxed for 1 hour. After solvent elimination, the reaction mixture was purified by column chromatography with ethyl acetate and ethyl acetate:methanol (10:2), as mobile phases. Yield: 11%. Mp.: 142.2-150.8° C. ESI-MS (m/z)=315 (M.+1).sup.+.

EXAMPLE 8

N1-[2-(methylamino)ethyl]-N4-(1-naphthyl) succinimide (8a)

(15) A slurry of activated molecular sieves 4 Å (500 mg) and CsOH.H.sub.2O (280 mg, 1.7 mmol) in 8 mL of anhydrous DMF, was stirred for 10 minutes. Next, compound 6 (485 mg, 1.7 mmol) in 1 mL of anhydrous DMF was added to maintain stirring for 30 min. at room temperature. To this reaction mixture, CH.sub.3I (124 μL, 2 mmol) in 0.5 mL of anhydrous DMF was added and stirred for 24 h., at room temperature. The mixture was thus filtered and rotoevaporated to dryness. The crude product was washed with NaOH (1N) and extracted with ethyl acetate. The organic phase was dried with Na.sub.2SO.sub.4 and purified by column chromatography with ethyl acetate as mobile phase. Yield: 70%. Mp.: 120° C. (dec.). ESI-MS (m/z)=300 (M.+1).sup.+.

EXAMPLE 9

Sodium Salt of the Acid Methyl (2-([4-(1-naphthylamine)-4-oxobutanoil]amino)ethyl)carbamoditionic (8b)

(16) Compound 8a (299 mg, 1 mmol) was added to a suspension of NaOH (80 mg, 2 mmol) in 3 mL of dry diethyl ether. The reaction mixture was cooled in an ice bath and stirred vigorously for 30 min., to slowly drop CS.sub.2 (121 μL, 2 mmol) in 0.5 mL of ether. Then, the mixture was stirred for 30 min. in cold and then, at room temperature for 2 hours. Solids were filtered and washed with dry diethyl ether. Yield: 75%. Mp.: (dec.). ESI-MS (m/z)=398 (M.+1).sup.+.

EXAMPLE 10

N1-(2-aminoethyl)-N4-(1-naphthyl) succinimide-131I (9)

(17) Labeling with .sup.131I: To a tube with Iodogeno covered walls (the tubes were impregnated with 250 to 500 μL of a Iodogeno solution (0.2 mg/mL in CHCl.sub.3), under in dry nitrogen atmosphere) was added 503.2 MBq (13.6 mCi) of .sup.131I and stirred for 10 min. at room temperature. Then 100 μL of a solution of 6 (7.7 10.sup.−3 mol/L) in PBS (pH 8.5) was added and the reaction mixture was thus stirred for another 15 minutes. The mixture was decanted in order to remove the .sup.131I free by filtration through filters of 3 MM Whatman paper impregnated with silver nitrate.

EXAMPLE 11

6-bromo-2-methoxynaphthalene (11)

(18) 6-Bromo-2-naphthol (10) was obtained from the reaction between 2-naphthol and molecular bromine in glacial acetic acid according to procedure described by Reddy et al. in Organic Process Research and Development, 1999, 3, 121-25.

(19) To a solution of Cs.sub.2CO.sub.3 (7.55 g, 23.3 mmol) and 6-bromo-2-naphthol (4.6 g, 17.9 mmol) in 45 mL of acetone, (CH.sub.3).sub.2SO.sub.4 (2.2 mL, 23.3 mmol) was added dropwise and stirred for 30 min. at room temperature. The reaction mixture was rotoevaporated and the crude was washed with water and extracted with CHCl.sub.3. The organic phase was dried with MgSO.sub.4 and cooled to precipitate 4.45 g of a white solid. Yield: 91%. Mp.: 101.4-103.7° C. (lit.: 103-105° C.).

EXAMPLE 12

3-(6-methoxy-2-naphthyl)propyl 4-methylbenzenesulfonate (13)

(20) Preparation of Grignard Reagent: According to general procedure described by Kidwell et al. in Organic Synthesis, Coll., 1973, 5, 918. In particular, in this invention, the reagent obtaining process was carried out in a flask with Mg (0.363 g, 14.95 mmol) and a small crystals of I.sub.2, previously flame-dried and the atmosphere replaced with dry Ar. Then, 1 mL (0.709 g, 2.99 mmol) of a solution of 11, in 3 mL of THF, was added dropwise to the flask. The reaction mixture was slowly heated to reflux until the boiling becomes spontaneous and a white sludge was formed. After that, the rest of the solution was added dropwise and refluxed for 4 h. until the formation of 12.

(21) Preparation of the Catalyst Li.sub.2CuCl.sub.4:

(22) According to general procedure described by Burns et al., in J. Chem. Soc. 1997, 119, 2125-2133.

(23) To a flask, previously flame-dried and evacuated with Ar, a solution of 1,3-propanediol di-p-tosylate (PrDiTs) (1.26 g, 3.289 mmol) in 1 mL of THF was added. Then, 1.79 mL of catalyst Li.sub.2CuCl.sub.4 was added. The reaction mixture was cooled at −30° C. and the Grignard reagent was added dropwise. Once the addition process was finished, the mixture was maintained at 8° C. for 24 h. and later at room temperature for 48 hours. The product was thus purified by column chromatography with a mixture of n-hexane:dichloromethane (100:0 to 80:20) as mobile phase. Yield: 15%. Mp.: dec. ESI-MS (m/z)=371 (M+1).sup.+.

EXAMPLE 13

2-(3-fluoropropyl)-6-methoxynaphthalene (14)

(24) 3 mL of (bmim)(BF.sub.4) was added to 3 mL of a solution of H.sub.2O (90 μL, 5 mmol) in CH.sub.3CN with 13 (370 mg, 1 mmol). Then, anhydrous CsF (760 mg, 5 mmol) was added. The reaction mixture was stirred at 100° C. for 2 hours. Upon completion of the reaction, the product of interest was extracted with diethyl ether (3×5 mL). The organic phase was dried (MgSO.sub.4) and concentrated to dryness to purify by column chromatography (ethyl acetate:hexane as mobile phase). Yield: 40%. Mp.: dec. ESI-MS (m/z)=219 (M+1).sup.+.

EXAMPLE 14

Labeling Studies and Biodistribution in Rats. Compound: N1-(2-aminoethyl)-N4-(1-naphthyl) succinimide-131I (9)

(25) Determination of Partition Coefficients: A solution of 9 (20 μL), prepared as described in example 10, was added to a mixture of 3 ml of n-octanol and 3 ml of distilled water. After stirring and leaving to stand the mixture, aliquots of 20 μL from each phase were taken to determine the radiometric distribution ratio by an activity meter (CRC 35R, Capintec Inc.). This procedure was repeated to the radiopharmaceutical of .sup.99mTc-ECD as reference, which is used for cerebral perfusion studies. Partition coefficient of 9: 0.54 (logP=−0.27) and .sup.99mTc-ECD: 40.6 (logP=1.6).

(26) Animal Studies: A solution of 9 15 MBq (407 Ci), prepared as described above, was administered to male Wistar rats (160 g, n=3) through the lateral tail vein. Then, images were taken every 15 seconds, for 30 min. (120 images) with a gamma camera (Medis Nucline TH22, Hungary), with a peak centered at 360 keV and a window of ±25%. The image processing was performed on a processing station Segami (USA).