Processes for preparing medicaments for the treatment of cardiovascular diseases and intermediates for use therein

Abstract

The present invention provides a compound of formula N wherein: X is CH.sub.2, oxygen or sulphur; R.sub.1, R.sub.2 and R.sub.3 are the same or different and signify hydrogens, halogens, alkyl, alkyloxy, hydroxy, nitro, alkylcarbonylamino, alkylamino or dialkylamino group, wherein N is in the form of the individual R- and S-enantiomer or a mixture of the (R)- and (S)-enantiomer. The present invention also provides a compound of formula MA. The present invention also provides processes for preparing the above compounds, and processes involving their use. The compounds are particularly useful as intermediates in the synthesis of peripherally-selective inhibitors of dopamine--hydroxylase. ##STR00001##

Claims

1. A process for preparing the (R)-enantiomer (R-N) or the (S)-enantiomer (S-N), the process comprising subjecting a compound of formula M to reduction using a reductase enzyme, wherein: X is CH.sub.2, oxygen or sulphur; and one of R.sub.1, R.sub.2 and R.sub.3 is hydrogen and the others are fluorine: ##STR00050##

2. The process of claim 1, wherein the compound M has the formula MB, the process further comprising reacting a compound of formula R with 2-nitroethanol or nitroethylene to obtain the compound MB: ##STR00051##

3. The process according to claim 2, wherein the compound R has the formula RA, comprising reacting a compound of formula RA to form a compound of formula MA: ##STR00052##

4. The process according to claim 1, wherein compound M has the formula MA: ##STR00053##

5. The process according to claim 1, wherein the enantiomer of the compound formula N is converted to the corresponding enantiomer of the compound of formula Q, or a salt thereof, by hydrogenation: ##STR00054## wherein: X is CH.sub.2, oxygen or sulphur; and one of R.sub.1, R.sub.2 and R.sub.3 is hydrogen and the others are fluorine.

6. The process according to claim 1, wherein the compound R-N has the formula R-NA and the method of converting the compound R-NA to the (R)-enantiomer of compound Q, which has the formula R-QA or a salt thereof: ##STR00055##

7. The process according to claim 6, wherein the compound of formula R-QA is converted to the L-tartrate salt thereof.

8. The process according to claim 5, wherein the hydrogenation comprises the use of hydrazine hydrate and Raney-Nickel; the use of Raney-Nickel under a hydrogen atmosphere; the use of palladium under a hydrogen atmosphere; or the use of palladium and formic acid, ammonium formate, or hydrazine hydrate.

9. The process of claim 5, further comprising preparing the (R)- or (S)-enantiomer of a compound of formula E or a salt thereof, ##STR00056## the process comprising reacting the corresponding (R)- (S)-enantiomer of the compound of formula Q as defined in claim 5 with a compound of formula D2 with a water soluble thiocyanate salt in the presence of an organic acid in a substantially inert solvent, ##STR00057## wherein n signifies 1, 2 or 3, R.sub.12 signifies hydrogen, alkyl or alkylaryl group, R.sub.11 signifies a hydroxyl protecting group and R.sub.13 signifies an amino protecting group, or R.sub.11 is defined as above but R.sub.12 and R.sub.13 taken together represent a phthalimido group; followed by subsequent deprotection of the intermediate products F to I: ##STR00058## to produce the respective (R)- or (S)-enantiomer of the compound of formula E or salt thereof.

10. The process according to claim 9, wherein the compound E is (R)-5-(2-aminoethyl)-1(6,8-difluorochroman-3-yl)-1,3-dihydroimidazole-2-thione or (R)-5-(2-aminoethyl)-1-(6,8-difluorochroman-3-yl)-1,3-dihydroimidazole-2-thione hydrochloride.

11. The process according to claim 9, wherein the compound E is (S1-5-(2-aminoethyl)-1-(5,7-difluoro-1,2,3,4-tetrahydronaphthalen-2-yl)-1,3-dihydroimidazole-2-thione; (R)-5-(2-aminoethyl)-1-(6,7-difluorochroman-3-yl)-1,3-dihydrohnidazole-2-thione; (S)-5-(2-aminoethyl)-1-(6,8-difluorochroman-3-yl)-1,3-dihydroimidazole-2-thione; (R)-5-aminomethyl-1-(6,8-difluorochroman-3-yl)-1,3-dihydroimidazole-2-thione; (R)-5-(3-aminopropyl)-1-(6,8-difluoroehroman-3-yl)-1,3-dihydroimidazole-2-thione; (S)-5-(3-aminopropyl)-1-(5,7-difluoro-1,2,3,4-tetrahydronaphthalen-2-yl)-1,3-dihydroimidazole-2-thione; or (R)-1-(6,8-difluorochroman-3-yl)-5-(2-methylaminoethyl)-1,3-dihydroimidazole-2-thione or a salt thereof.

12. The process according to claim 11, wherein the salt is the hydrochloride salt.

13. The process of claim 9, further comprising preparing the individual (R)- or (S)-enantiomer or a mixture of the (R)- and (S)-enantiomers or a pharmaceutically acceptable salt of a compound of formula Y, which process comprises reacting the (R)- or (S)-enantiomer or a mixture of the (R)- and (S)-enantiomers of a compound of Formula E with a compound of formula IX under reductive alkylation conditions, ##STR00059## wherein X is CH.sub.2, oxygen or sulphur; and one of R.sub.1, R.sub.2 and R.sub.3 is hydrogen and the others are fluorine; R.sub.4 signifies -alkyl-aryl or -alkyl-heteroaryl; R.sub.5 signifies aryl or heteroaryl, n is 2 or 3; wherein the term alkyl means hydrocarbon chains, straight or branched, containing from one to six carbon atoms, optionally substituted by aryl, alkoxy, halogen, alkoxycarbonyl or hydroxycarbonyl groups; the term aryl means a phenyl or naphthyl group, optionally substituted by alkyl, alkyloxy, halogen or nitro group; the term halogen means fluorine, chlorine, bromine or iodine; the term heteroaryl means heteroaromatic group.

14. The process according to claim 13, wherein the compound of formula Y is a compound of formula X: ##STR00060## its (R)- or (S)-enantiomer, or mixture of the (R)- and (S)-enantiomer, or a pharmaceutically acceptable salt thereof.

15. The process according to claim 14, wherein the compound is the (R)-enantiomer of the compound of Formula X.

16. The process according to claim 14, comprising the hydrochloride salt of the compound of formula X.

17. The process of claim 5, further comprising preparing the (R)-enantiomer or a pharmaceutically acceptable salt of a compound of formula YA (R-YA), which wherein process comprises reacting a salt of the (R)-enantiomer of the compound of formula QA (R-QA) with a compound of formula C, to obtain a compound of formula V and converting the compound of formula V to the compound of formula R-YA: ##STR00061## wherein the salt of compound R-QA is selected from L-tartrate, hydrochloride, mesylate, tosylate, trifluoroacetate, citrate, glycolate and oxalate.

18. The process according to claim 17, wherein the salt of compound R-QA is the L-tartrate salt.

19. The process of claim 5, further comprising preparing the (R)-enantiomer or a pharmaceutically acceptable salt thereof of a compound of formula YA (R-YA), which process comprises reacting a salt of the (R)-enantiomer of the compound of Formula QA (R-QA) with a compound of formula VI, to obtain a compound of formula VII and converting the compound of formula VII to the compound of formula R-YA: ##STR00062## wherein Ns signifies o-nitrophenylsulphonyl and the salt of compound R-QA is selected from L-tartrate, hydrochloride, mesylate, tosylate, trifluoroacetate, citrate, glycolate and oxalate.

20. The process according to claim 19, wherein the salt of compound R-QA is the L-tartrate salt.

Description

EXAMPLES

Example 1

Nitro Chromene Synthesis

(1) ##STR00045##

(2) To 3,5-difluoro-2-hydroxybenzaldehyde (10 g, 63 mmol, 1 eq), di-n-butylamine (4.1 g, 32 mmol, 0.5 eq), phtalic anhydride (18.7 g, 126 mmol, 2 eq) in toluene (500 mL) was added nitroethanol (5.75 g, 63 mmol, 1 eq). The round bottomed flask fitted with a dean stark apparatus was refluxed for 18 h. The mixture was cooled and nitroethanol (5.75 g, 63 mmol, 1 eq) was added. The resulting reaction mixture was then reflux for 12 h. After cooling, the solution was evaporated down to approximately 150 mL and purified over silica gel (eluent ethyl acetate:hexane 1:1) this gave several fractions that contained only the product by TLC, these was evaporated under reduced pressure to yield 1.8 g which was 100% pure by HPLC area. Several more fractions were collected containing a mixture of product and starting material. These were combined and washed with 2% NaOH solution (250 mL) to remove starting material. The organic layer was washed with water (50 mL), dried over sodium sulfate and evaporated under reduced pressure to give 2.49 g of brown solid (100% pure by HPLC area). More fractions were collected. These were combined, washed with 2% NaOH solution (3100 mL), water (100 mL) and dried over sodium sulfate. This was then filtered and evaporated down in vacuum to yield 6.14 g of a brown solid which was 91.3% pure by HPLC area. 6,8-difluoro-3-nitro-2H-chromene (9.90 g, 73.4%) was obtained as a brown solid.

Example 2

Nitro Chromene Synthesis with Column Purification

(3) To a solution of isobenzofuran-1,3-dione (4.68 g, 31.6 mmol), 3,5-difluoro-2-hydroxybenzaldehyde (2.5 g, 15.81 mmol) in Toluene (25 ml) was added 2-nitroethanol (2.88 g, 31.6 mmol). The resulting mixture was heated to reflux overnight (Dean stark).

(4) The reaction conversion was checked by TLC (eluent PE/EtOAc 9:1). A yellow spot was observed and corresponds to the expected product.

(5) Reaction was cooled to room temperature and a plug of silica gel was performed. A pale brown solid (3.9 g) was obtained. .sup.1H-NMR showed presence of product and starting material. The solid was dissolved in diethylether and the organic layer was washed with aqueous sodium carbonate, dried over Na.sub.2SO.sub.4, filtered and concentrated under reduced pressure. A pale brown solid (1.7 g,) was obtained. The .sup.1H-NMR was indicated no starting material but still polymer from nitroethanol and residue of phtalic anhydride. A second silica plug (eluent: PE/EtOAc 95:5) was done. A pale yellow solid (1.5 g) was obtained. .sup.1H-NMR of solid showed only product and polymer. The solid was recrystallized from methanol/water. A pale yellow solid (1.05 g, 31.2%) was obtained.

Example 3

Nitro Chromene Synthesis without Column Purification

(6) To a solution of isobenzofuran-1,3-dione (18.74 g, 127 mmol), 3,5-difluoro-2-hydroxybenzaldehyde (10 g, 63.3 mmol) in Toluene (100 ml) was added 2-nitroethanol (6.86 ml, 95 mmol). The resulting mixture was heated to reflux for 24 h (Dean stark).

(7) The reaction conversion was checked by HPLC and by .sup.1H-NMR. Only 50% conversion was obtained.

(8) The reaction mixture was cooled to room temperature and diluted with DCM (100 mL) and 1M NaOH solution (200 mL).

(9) The biphasic system was stirred for 30 minutes and then separated (very difficult to see phase separation). The aqueous layer was washed with DCM (50 mL) and the combined organic layers were washed twice with water (250 ml), dried over sodium sulfate. The filtered organic layer was concentrated under reduced pressure. To the residue was added methanol (50 mL). The methanol was then removed by distillation under reduced pressure. A brown solution precipitated when most of the methanol was removed. More methanol was added and more solid crushed out then few drops of water was added to increase the product precipitation. The brown slurry was stirred for 30 minutes and filtered. The brown solid was washed with methanol/water (1:9, 5 mL) and dried in a vacuum oven at 40 C. for 12 h. 6,8-difluoro-3-nitro-2H-chromene (4.9 g, 22.99 mmol,) was obtained as brown solid in 36.3% yield.

(10) HPLC showed a purity of 98% and .sup.1H-NMR confirmed the structure and purity around 95%

Example 4

Reduction of Nitro Chromene to Nitro-alkane (Racemic Mixture)

(11) ##STR00046##

(12) To a suspension of 6,8-difluoro-3-nitro-2H-chromene (213 mg, 0,999 mmol) and silica (0.8 g, 0,999 mmol) in a mixture of CHCl.sub.3 (10 ml) and IPA (3.4 ml) at 0 C. was added portion wise sodium borohydride (95 mg, 2,498 mmol). The resulting mixture was stirred at 0 C. for 45 minutes. Reaction conversion was checked by HPLC. 1 mL of acetic acid was added at 0 C. and the resulting mixture was stirred for 30 minutes at room temperature. The slurry was filtered and the silica was washed with DCM. The filtrate was diluted with ethyl acetate and water and the biphasic system was separated. The aqueous layer was back extracted with ethyl acetate. The combined organic layers were washed with brine, dried over MgSO.sub.4, filtered and concentrated under reduced pressure.

(13) 6,8-difluoro-3-nitrochroman (196 mg, 0,911 mmol, 91% yield) was obtained as a pale yellow oil.

Example 5

Preparation of 6,8-difluorochroman-3-one from nitro chromene

(14) ##STR00047##

(15) A solution of 6,8-difluoro-3-nitro-2H-chromene (100 mg, 0,469 mmol) in acetic acid (0.5 ml) is added slowly to a stirred slurry of iron (262 mg, 4.69 mmol) in acetic acid (1 ml) at 60deg. C. The reaction mixture is stirred at 60 C. for 2 hour then allowed to cool to room temperature and stirred overnight. The reaction mixture is poured onto ice-water (30 ml) and filtered through Celite. The solid was wash with dichloromethane (DCM) (50 ml). The organic portion is separated and washed with water (230 ml) and brine (30 ml), dried over MgSO.sub.4, filtered and concentrated in vacuo to give a brown oil. 6,8-difluorochroman-3-one (75 mg, 0,407 mmol, 87% yield) was obtained as a brown oil.

Example 6

Preparation of 6,8-difluorochroman-3-one from methyl 6,8-difluoro-2H-chromen-3-yl-carbamate

(16) ##STR00048##

(17) Methanol (1000 m ml) was added to a slurry of methyl 6,8-difluoro-2H-chromen-3-yl-carbamate (250 g, 1.037 mol) in hydrogen chloride 6N (2000 ml, 12 mol) at room temperature. The resulting mixture was reflux and stirred for 2 hours. Reaction monitored by HPLC.

(18) Reaction was not complete but was stopped in order to avoid degradation of the product. The yellow solution was cooled to room temperature. A slurry (two type of solid) was observed and diluted with diethyl ether (300 mL). The resulting slurry was stirred at 5 C. for 1 hour then filtered. The yellow solid was washed with water. The resulting wet yellow solid was suspended in diethylether (400 mL) and petroleum ether (PE) (400 mL) was added. Slight yellow solid was stirred at room temperature overnight, filtered and washed with PE (300 mL), dried in a vacuum oven at 30 C. for 4 h. The wet sample was checked by NMR. No starting material was detected. A pale yellow solid (72.5 g, solid 1) was obtained. The mother liquors were concentrated to dryness. A yellow solid was obtained, suspended in diethyl ether and PE. The slurry was then stirred for 4 hours, filtered, washed with PE. A dark yellow solid (4.5 g, solid 2) was obtained. Solid 1 (2 g) was diluted in DCM and washed with water (pH=6). The organic layer was then dried over Na.sub.2SO.sub.4, filtered, concentrated to dryness. A crystalline pale yellow solid (1.9 g, solid 3) was obtained. NMR showed the same purity for solid 3 as for solid 1. The remaining part of solid 1 was then diluted in DCM. The resulting organic layer was washed with water, dried over Na.sub.2SO.sub.4, filtered and then concentrated to dryness. Slight yellow crystalline solid (68.5 g, solid 4) was obtained. NMR confirmed high quality material.

(19) Loss on Drying (LOD): 1.03%.

Example 7

Biotransformation: Transaminases

(20) ##STR00049##

(21) Codexis transaminases ATA-025, ATA-251 and ATA-P2-A07 recognized 6,8-difluorochroman-3-one as the substrate and produced the corresponding 6,8-difluorochroman-3-amine. Experimental protocol

(22) Preparation of triethanolamine buffer solution 200 mM (Solution 1):

(23) Dissolve 14.9 g of triethanolamine in 500 mL of deionized water. Adjust pH to 7.5 by adding conc. HCl.

(24) Preparation of 2.5M isopropylamine hydrochloride solution (Solution 2):

(25) Dissolve 20.8 mL of conc. HCL in 40 mL. At 0 C., add isopropylamine (20.5 mL) drop wise over 1.5 hours and finally complete the volume to 100 mL with deionized water. The resulting pH is 4.

(26) Preparation of PLP buffer solution (Solution 3, prepare in the day of experiment)

(27) Dissolve 4.8 mg PLP in 20 mL of triethanolamine solution

(28) General Protocol: Weight 5 mg of each enzyme in a vial Add 500 L of PLP solution (Solution 3) Add 400 L of 2.5M iPrNH.sub.2HCl (Solution 2) Add 15 mg of ketone Add 190 L of buffer (Solution 1) Add 20 L of DMSO Stir the mixture overnight at 30 C. 400 L of ethyl acetate was added to all the vials after overnight reaction. The biphasic system was stirred for 10 minutes and allowed to separate and TLC was done on organic layer. Eluent: Petroleum Ether/ethyl acetate 7:3 and DCM/MeOH 9:1. Results ATA-025: No starting material by TLC; produced (S)-6,8-difluorochroman-3-amine; Chiral HPLC: 72.8% ee. ATA-251: No starting material by TLC; produced (R)-6,8-difluorochroman-3-amine; Chiral HPLC: 50% ee. ATA-P2-A07: No starting material by TLC; produced (S)-6,8-difluorochroman-3-amine; Chiral HPLC: 99.0% ee.

Example 8

Solubility Study

(29) The solubility of non-micronized and micronized (R)-5-(2-(benzylamino)ethyl)-1-(6,8-difluorochroman-3-yl)-1H-imidazole-2(3H)-thione in several organic solvents was determined.

(30) Solubility Solubility was evaluated according to Eur. Ph. Chapter 5.11 at room temperature.

(31) A comparison between the results obtained before and after micronization shows no overall significant changes in the solubility profile.

(32) The following descriptions are used to describe the degree of solubility:

(33) TABLE-US-00001 Approximate parts of solvent for Description one part of solute Very soluble less than 1 part Freely soluble from 1 to 10 parts Soluble from 10 to 30 parts Sparingly from 30 to 100 parts soluble Slightly soluble from 100 to 1000 parts Very slightly from 1000 to 10,000 parts soluble Practically greater than or equal to 10,000 parts insoluble

(34) The (R)-5-(2-(benzylamino)ethyl)-1-(6,8-difluorochroman-3-yl)-1H-imidazole-2(3H)-thione was soluble to some extent (mostly either sparingly soluble, slightly soluble or very slightly soluble) in most of the polar organic solvents tested. The (R)-5-(2-(benzylamino)ethyl)-1-(6,8-difluorochroman-3-yl)-1H-imidazole-2(3H)-thione was soluble to some extent (either sparingly soluble, slightly soluble or very slightly soluble) in all of the polar organic aprotic solvents tested.

(35) The description of the solubilities of the non-micronized particles is shown below:

(36) TABLE-US-00002 Solvent Description 1,4-Dioxane Slightly soluble 2-propanol Insoluble Absolute ethanol Practically insoluble Acetone Slightly soluble Acetonitrile Very slightly soluble Chloroform Very slightly soluble Cyclohexane Insoluble Dichloromethane Slightly soluble Dimethylformamide Sparingly soluble DMSO Sparingly soluble Ethyl acetate Very slightly soluble Hexafluoroisopropanol Sparingly soluble Iso-octane (2,2,4- Insoluble trimethylpentane) Isopropyl acetate Very slightly soluble Methanol Very slightly soluble Methanol or acetonitrile Sparingly soluble acidified with 0.1% formic acid or TFA Methyl ethyl ketone Slightly soluble N,N-methylpirrolidone Sparingly soluble Tetrahydrofuran Sparingly soluble Toluene Very slightly soluble Trifluoroethanol Slightly soluble

(37) The description of the solubilities of the micronized particles is shown below:

(38) TABLE-US-00003 Solvent Description 1,4-Dioxane Very slightly soluble 2-propanol Insoluble Absolute ethanol Very slightly soluble Acetone Slightly soluble Acetonitrile Very slightly soluble Chloroform Slightly soluble Cyclohexane Insoluble Dichloromethane Very slightly soluble Dimethylformamide Sparingly soluble DMSO Slightly soluble Ethyl acetate Very slightly soluble Iso-octane (2,2,4-trimethylpentane) Practically insoluble Methanol Very slightly soluble Methanol or acetonitrile acidified Slightly soluble with 0.1% formic acid or TFA Methyl ethyl ketone Slightly soluble N,N-methylpirrolidone Sparingly soluble Tetrahydrofuran Sparingly soluble

(39) The aqueous solubility of (R)-5-(2-(benzylamino)ethyl)-1-(6,8-difluorochroman-3-yl)-1H-imidazole-2(3H)-thione was determined in triplicate at 37 C. Aqueous solutions of HCl (pH 1.2, 2.0, 3.0), potassium chloride (pH 1.2, 2.0), acid phthalate (pH 3.0), acetate (pH 4.5, 5.5), phosphate (pH 7.4) and boric acid (pH 9.0) were tested. It was seen that the solubility of (R)-5-(2-(benzylamino)ethyl)-1-(6,8-difluorochroman-3-yl)-1H-imidazole-2(3H)-thione (both non-micronized and micronized) decreases with the increase of pH. Maximum solubility was achieved by using HCl 0.01 (pH 2.0); further increase in pH resulted in solubility decrease. There was no considerable improvement in solubility after micronization. In fact, solubility in HCl 0.01 (pH 2.0) is lower.

Example 9

Particle Size Study

(40) The particle size distribution of (R)-5-(2-(benzylamino)ethyl)-1-(6,8-difluorochroman-3-yl)-1H-imidazole-2(3H)-thione was determined by laser diffraction.

(41) Particle size determination experiments were performed in a Malvern Mastersizer 2000 laser difractometer equipped with a wet dispersion unit Hydro 2000S. The analytical information obtained was acquired and processed with the software Malvern Mastersizer 5.54.

(42) The following instrumental settings were used:

(43) TABLE-US-00004 Equipment Malvern Mastersizer 2000 Material Sample (R) -5-(2- (benzylamino)ethyl)-1- (6,8-difluorochroman-3- yl)-1H- imidazole-2(3H)- thione Dispersant Cyclohexane with surfactant; refractive index 1.426 Measurement Background time 15 seconds Measurement time 30 seconds Pump/Stirrer speed 2500 rpm Dispersant level 15% threshold

(44) The results are summarised below.

(45) The particle size distribution was measured on samples both before micronization and after micronization.

(46) A volume weighted distribution was obtained for the samples. The contribution of each particle in the distribution relates to the volume of that particle, i.e. the relative contribution will be proportional to (size).sup.3.

(47) The parameters (D.sub.vX) are reported below based on the maximum particle size for a given percentage volume of the sample. In DOC, D stands for diameter, v indicates a volume distribution weighting, and X is the percentage of sample below this particle size. For example, the D.sub.v50 would be the maximum particle diameter below which 50% of the sample volume exists.

(48) Three samples of non-micronized particles of (R)-5-(2-(benzylamino)ethyl)-1-(6,8-difluorochroman-3-yl)-1H-imidazole-2(3H)-thione were tested.

(49) The D.sub.v10 figure for the samples ranges from around 30 m to around 150 m.

(50) The D.sub.v50 figure for the samples ranges from around 200 m to around 300 m.

(51) The D.sub.v90 figure ranges from around 400 m to around 600 m.

(52) Nine samples of one micronized batch of (R)-5-(2-(benzylamino)ethyl)-1-(6,8-difluorochroman-3-yl)-1H-imidazole-2(3H)-thione were tested.

(53) The D.sub.v10 figure for the samples ranges from around 3 m to around 8 m.

(54) The D.sub.v50 figure for the samples ranges from around 20 m to around 50 m.

(55) The D.sub.v90 figure ranges from around 100 m to around 350 m.

(56) It will be appreciated that the invention may be modified within the scope of the appended claims.