DIHYDROPYRIDINES

Abstract: 1,4,dihydropyridine derivatives of the formula (I):- where R is an optionally substituted aryl or heteroaryl group; R¹ and R² are each independently C₁-C₄ alkyl or 2-methoxyethyl; Y is -(CH₂) n where n is 2,3 or 4, -CH₂CH(CH₃)- or -CH₂C(CH₃)₂- and m is 0, 1 or 2. The compounds are useful in the treatment of hypertension.

Description: This invention relates to certain dihydropyridines, specifically to certain 1,4-dihydropyridines having a hydroxy substituent in a thioether side chain attached to the 2-position, and derivatives thereof, which have utility as anti-ischaemic and antihypertensive agents. The compounds of the invention reduce the movement of calcium into the cell and they are thus able to delay or prevent the cardiac contracture which is believed to be caused by an accumulation of intracellular calcium under ischaemic conditions. Excessive calcium influx during ischaemia can have a number of additional adverse effects which would further compromise the ischaemic myocardium. These include less efficient use of oxygen for ATP production, activation of mitochondrial fatty acid oxidation and possibly, promotion of cell necrosis. Thus the compounds are useful in the treatment or prevention of a variety of cardiac conditions, such as angina pectoris, cardiac arrhythmias, heart attacks and cardiac hypertrophy. The compounds also have vasodilator activity since they can inhibit calcium influx in cells of vascular tissue and they are thus also useful as antihypertensive agents and for the treatment of coronary vasospasm. According to the specification of our co-pending European patent application publication no. 161 917 there are described and claimed a number of dihydropyridine anti-ischaemic and anti hypertensive agents wherein the 2-position of the dihydropyridine ring is substituted with hydroxyalkoxymethyl groups. We have now discovered a further related series of dihydropyridine compounds having valuable therapeutic properties wherein the substituent in the 2 position is a hydroxy alkylthiomethyl group. According to the invention, there are provided novel 1,4-dihydropyridine derivatives of the formula:- where R is an optionally substituted aryl or heteroaryl group; R¹ and R² are each independently C₁-C₄ alkyl or 2-methoxyethyl; Y is -(CH₂) n - where n is 2,3 or 4, -CH₂CH(CH₃)- or -CH₂C(CH₃)₂-; and m is 0, 1 or 2. The term "aryl" as used in this specification includes unsubstituted phenyl and phenyl substituted by, for example, one or two substituents each independently selected from nitro, halo, C₁-C₄ alkyl, C₁-C₄ alkoxy, hydroxy, trifluoromethyl and cyano. It also includes 1- and 2-naphthyl. "Halo" means F, Cl, Br or I. The term "heteroaryl" as used in this specification for R means an aromatic heterocyclic group which may optionally be substituted and includes, for example, benzofuranyl; benzothienyl; pyridyl optionally substituted by methyl, methylthio, halo or cyano; quinolyl; benzoxazolyl; benzothiazolyl; furyl; pyrimidinyl; thiazolyl; 2,1,3-benzoxadiazol-4-yl; 2,1,3-benzothiadiazol-4-yl; and thienyl optionally monosubstituted by halo or C₁-C₄ alkyl. Alkyl and alkoxy groups having 3 or more carbon atoms can be straight or branched chain. R is preferably phenyl substituted by 1 or 2 substituents selected from halo and CF₃, or is 2-chloropyrid-3-yl. R is most preferably 2-chlorophenyl or 2,3-dichlorophenyl. R¹ and R² are preferably CH₃ or C₂H₅. Most preferably, R¹ is CH₃ and R² is C₂H₅, or R¹ and R² are both CH₃. Y is preferably -(CH₂)₂-, -(CH₂)₄-, -CH₂CH(CH₃)- or -CH₂C(CH₃)₂-, most preferably -(CH₂)₂-. Preferred compounds of the present invention are 4-(2,3-­ dichlorophenyl)-3-ethoxycarbonyl-2-[(2-hydroxyethyl)-thiomethyl]-­ 5-methoxycarbonyl-6-methyl-1,4-dihydropyridine, and 3,5-bis (methoxycarbonyl)-4-(2-chlorophenyl)-2-[(2-hydroxyethyl)-­ thiomethyl]-6-methyl-1,4-dihydropyridine. The compounds of the formula (I) containing one or more asymmetric centres will exist as one or more pairs of enantiomers, and such pairs or individual isomers may be separable by physical methods, e.g. by fractional crystallisation or chromatography of the parent compounds or suitable derivatives thereof as will be known to those skilled in the art. The invention includes the separated pairs as well as mixtures thereof, as racemic mixtures or as separated optically-active isomeric forms. The compounds of the invention in which m is 0 can be prepared by reacting a compound of the formula: wherein R, R¹ and R² are as previously defined and Q is a good leaving group, with a thiol of the formula: HS-Y-OH--- (III) wherein Y is as previously defined. The leaving group Q may be for example a halo atom, preferably bromo, or a para-toluenesulphonyloxy, methanesulphonyloxy, trifluoromethanesulphonyloxy or l-imidazolylsulphonyloxy group. The reaction with the thiol of formula (III) is generally achieved by stirring the reactants in more or less equimolar proportions in an inert organic solvent e.g. tetrahydrofuran or N,N-dimethylformamide, in the presence of a base, e.g. potassium carbonate. The reaction is generally complete within a few hours at room temperature and the desired product is then isolated and purified using conventional techniques. The compounds of the formula (I) in which m is 1 or 2, (i.e. the sulphinyl and sulphonyl derivatives) can be prepared by the oxidation of the corresponding thioether compounds, typically by using about one equivalent of a suitable oxidising agent such as metachloroperbenzoic acid or sodium metaperiodate, to give the sulphinyl compounds, or two or more equivalents to give the sulphonyl derivatives. The starting materials of formula II are generally known compounds described in the literature or obtainable following literature precedents. Thus for example, in one process the corresponding 2-methyl-l,4-dihydropyridine may be halogenated to yield the corresponding compound of formula (II) wherein Q is halo. The reaction may for example be performed using pyridinium bromide perbromide to yield the 2-bromomethyl derivative. In an alternative process the corresponding 2-hydroxymethyl-1,4-dihydropyridine may be converted to, for example, the 2-halomethyl, 2-paratoluenesulphonyloxymethyl, 2-methanesulphonyl or 2-trifluoromethyloxymethyl derivative of formula (II) by conventional methods. Thus, for example, in one particular variant of this process, reaction of 2-hydroxymethyl-­ 1,4-dihydropyridine with sulphuryl chloride in N,N-dimethyl­ formamide followed by addition of imidazole initially yields the compound of formula (II) wherein Q is a 1-imidazolylsulphonyloxy group. This compound in fact breaks down by reaction with the dihydropyridine nitrogen atom to yield a cyclic sulphamate ester which is reacted with the thiol of formula (III). The ability of the compounds to inhibit the movement of calcium into the cell is shown by their effectiveness in reducing the contraction of vascular tissue in vitro which is the consequence of calcium influx caused by a high extracellular concentration of potassium ions. The test is performed by mounting spirally cut strips of rat aorta with one end fixed and the other attached to a force transducer. The tissue is immersed in a bath of physiological saline solution containing calcium ions at a concentration of 2.5 millimolar and potassium ions at a concentration of 5.9 millimolar. Potassium chloride solution is added to the bath with a pipette to give a final potassium ion concentration of 45 millimolar. The change in tension caused by the resulting contraction of the tissue is noted. The bath is drained and refilled with fresh saline solution containing the particular compound under test. After 45 minutes, the procedure is repeated and the contraction again noted. The concentration of compound required to reduce the response by 50% is determined. The antihypertensive activity of the compounds is evaluated after oral administration by measuring the fall in blood pressure in spontaneously hypertensive rats or renally hypertensive dogs. For administration to man in the curative or prophylactic treatment of cardiac conditions and hypertension, oral dosages of the compounds will generally be in the range of from 2-100 mg daily for an average adult patient (70 kg). Thus for a typical adult patient, individual tablets or capsules contain from 1 to 10 mg of active compound, in a suitable pharmaceutically acceptable vehicle or carrier. Dosages for intravenous administration would typically be within the range 1 to 10 mg per single dose as required. In practice the physician will determine the actual dosage which will be most suitable for an individual patient and it will vary with the age, weight and response of the particular patient. The above dosages are exemplary of the average case but there can, of course, be individual instances where higher or lower dosage ranges are merited, and such are within the scope of this invention. For human use, the compounds of the formula (I) can be administered alone, but will generally be administered in admixture with a pharmaceutical carrier selected with regard to the intended route of administration and standard pharmaceutical practice. For example, they may be administered orally in the form of tablets containing such excipients as starch or lactose, or in capsules or ovules either alone or in admixture with excipients, or in the form of elixirs or suspensions containing flavouring or colouring agents. They may be injected parenterally, for example, intravenously, intramuscularly or subcutaneously. For parenteral administration, they are best used in the form of a sterile aqueous solution which may contain other substances, for example, enough salts or glucose to make the solution isotonic with blood. Thus in a further aspect the invention provides a pharmaceutical composition comprising a compound of the formula (I) together with a pharmaceutically acceptable diluent or carrier. The invention also includes a compound of the formula (I) for use in medicine, in particular in the treatment of ischaemic heart disease, angina or hypertension in a human being. The preparation of the compounds of the invention is illustrated by the following Examples. EXAMPLE 1 4-(2,3-Dichlorophenyl)-3-ethoxycarbonyl-2-[(2-hydroxyethyl)-­ thiomethyl]-5-methoxycarbonyl-6-methyl-1,4-dihydropyridine Sulphuryl chloride (0.80 ml) was added dropwise over 10 minutes to stirred, ice-cooled N,N-dimethylformamide (15 ml) and the mixture then added over 40 minutes to a stirred, ice-cooled solution of 4-(2,3-dichlorophenyl)-3-ethoxycarbonyl-2-hydroxy­ methyl-5-methoxycarbonyl-6-methyl-1,4-dihydropyridine (2.00 g) and imidazole (0.85 g) in N,N-dimethylformamide (30 ml). The mixture was stirred at room temperature for 2.5 hours and evaporated. The residue was dissolved in ethyl acetate and the solution washed twice with 2M hydrochloric acid, dried over magnesium sulphate and evaporated. The residue was dissolved in a mixture of tetrahydrofuran (15 ml) and N,N-dimethylformamide (15 ml) and the solution added to a stirred solution of 2-mercaptoethanol (0.95 ml) in a mixture of tetrahydrofuran (15 ml) and N,N-­ dimethylformamide (15 ml) containing potassium carbonate (2.00 g). The mixture was stirred at room temperature for 2 hours and evaporated. The residue was partitioned between ethyl acetate and water and the layers separated. The organic layer was washed twice with water and once with saturated brine, dried over magnesium sulphate and evaporated. The residue was purified by chromatography on silica (10 g) using hexane plus 50-100% dichloromethane as eluant. Appropriate fractions were combined and evaporated and the residue crystallised from di-isopropyl ether to give the title compound (0.60 g), m.p. 125°C. Found: C,52.11; H,4.98; N,3.01. C₂₀H₂₃Cl₂NO₅S requires: C,52.17; H,5.03; N,3.04%. EXAMPLE 2 3,5-Bis(methoxycarbonyl)-4-(2-chlorophenyl)-2-[(2-hydroxyethyl)-­ thiomethyl]-6-methyl-1,4-dihydropyridine Pyridinium bromide perbromide (2.00 g) was added in one portion to a stirred, ice-cooled solution of 3,5-bis(methoxy-­ carbonyl)-4-(2-chlorophenyl)-2,6-dimethyl-1,4-dihydropyridine (1.68 g) and pyridine (0.80 ml) in dichloromethane (40 ml) and the mixture stirred at 0°C for 1.5 hours. The mixture was washed twice with ice-cold 0.5 M hydrochloric acid, dried over magnesium sulphate and evaporated without external heating. The residue was dissolved in tetrahydrofuran (15 ml) and the solution added to a stirred, ice-cooled solution of 2-mercaptoethanol (0.78 g) in tetrahydrofuran (20 ml) containing potassium carbonate (1.38 g). The mixture was stirred at 0°C for 2 hours and then at room temperature for 16 hours and then partitioned between ethyl acetate and water. The layers were separated and the organic layer washed with water, dried over sodium sulphate and evaporated. The residue was purified by chromatography on silica (17 g) using dichloromethane plus 0-50% ethyl acetate as eluant. Appropriate fractions were combined and evaporated to give the title compound (0.38 g) as an oil. Found: C,55.59; H,5.42; N,3.49. C₁₉H₂₂ClNO₅S requires C,55.41; H,5.35; N,3.40%.

Claims: 1. 1,4-dihydropyridine derivatives of the formula (I):- where R is an optionally substituted aryl or heteroaryl group; R¹ and R² are each independently C₁-C₄ alkyl or 2-methoxyethyl; Y is -(CH₂)n- where n is 2,3 or 4, - CH₂CH(CH₃)- or -CH₂C(CH₃)₂-; and m is 0, 1 or 2. 2. A compound of formula (I) as claimed in claim 1 wherein R is aryl and aryl is unsubstituted phenyl or phenyl substituted by, one or two substituents each independently selected from nitro, halo, C₁-C₄ alkyl, C₁-C₄ alkoxy, hydroxy, trifluoromethyl and cyano, or is 1- or 2-naphthyl; or wherein R is heteroaryl and heteroaryl is benzofuranyl; benzothienyl; pyridyl optionally substituted by methyl, methylthio, halo or cyano, quinolyl, benzoxazolyl; bezo­ thiazolyl; furyl; pyrimidinyl; thiazolyl; 2,1,3-benzoxadiazol-­ 4-yl; 2,1,3-benzothiadiazol-4-yl; and thienyl optionally monosubstituted by halo or C₁-C₄ alkyl. 3. A compound of formula (I) as claimed in claim 2 wherein R is 2-chlorophenyl or 2,3-dichlorophenyl. 4. A compound as claimed in any preceding claim wherein either R¹ is CH₃ and R² is C₂H₅ or R¹ is C₂H₅ and R² is CH₃. 5. A compound as claimed in any preceding claim wherein Y is -(CH₂)₂- and m is 0. 6. 4-(2,3-dichlorophenyl)-3-ethoxycarbonyl-2-[(2-hydroxy­ ethyl)thiomethyl]-5-methoxycarbonyl-6-methyl-1,4-dihydropyridine. 7. 3,5-Bis (methoxycarbonyl)-4-(2-chlorophenyl)-2-[(2-­ hydroxyethyl)-thiomethyl]-6-methyl-1,4-dihydropyridine. 8. A pharmaceutical composition comprising a compound of formula (I) as claimed in any preceding claim, together with a pharmaceutically acceptable diluent or carrier. 9. A compound of the formula (I) as defined in any one of claims 1 to 7, for use in medicine. 10. Use of a compound of the formula (I) as defined in any one of claims 1 to 7 in the manufacture of a medicament for the treatment of hypertension or ischaemia. CLAIMS FOR THE FOLLOWING CONTRACTING STATES: AT, ES, GR 1. A process for preparing 1,4-dihydropyridine derivatives of the formula (I):- where R is an optionally substituted aryl or heteroaryl group; R¹ and R² are each independently C₁-C₄ alkyl or 2-methoxyethyl; Y is -(CH₂)n- where n is 2,3 or 4, -CH₂CH(CH₃)- or -CH₂C(CH₃)₂-; and m is 0, 1 or 2. characterised by reaction of a compound of the formula (II): wherein R, R¹ and R² are as previously defined and Q is a good leaving group, with a thiol of formula (III). HS-Y-OH---(III) wherein Y is as previously defined to give a compound of formula (I) in which m is 0 followed by optionally oxidising the compound of formula (I) in which m is 0 to give a compound wherein m is 1 or 2. 2. A process as claimed in claim 1 wherein Q is a halo, para-toluenesulphonyloxy, methanesulphonyloxy, trifluoromethanesulphonyloxy or 1-imidazolylsulphonyloxy group. 3. A process as claimed in any preceeding claim wherein R is 2-chlorophenyl or 2,3-dichlorophenyl. 4. A process as claimed in any preceeding claim wherein R¹ is CH₃ and R² is C₂H₅ or R¹ is C₂H₅ and R² is CH₃. 5. A process as claimed in any prceeding claim wherein Y is -(CH₂)₂- and m is 0. 6. A process as claimed in any preceeding claim wherein the reaction is performed in the presence of a base. 7. A process as claimed in claim 6 wherein the base is potassium carbonate. 8. A process as claimed in claim 1 wherein the oxidising agent is present in an amount of one equivalent to give the sulphinyl compound or in an amount of two or more equivalents to give the sulphonyl derivatives. 9. A process as claimed in claim 1 wherein the oxidising agent is metachloroperbenzoic acid or sodium metaperiodate. 10. A process for preparing a pharmaceutical composition comprising mixing a compound of the formula (I) as defined in claim 1 with a pharmaceutically acceptable diluent or carrier.

Inventors: ALKER, DAVID, CAMPBELL, SIMON FRASER, CROSS, PETER EDWARD
Applicants: PFIZER LIMITED
Application year: 1986
Main classification: C07D211
IPC codes: C07D417, C07D401, C07D413, C07D211, C07D409, C07D405, A61P9, A61K31