CARBACYCLIN DERIVATIVES

Abstract: Carbacyclin derivatives with anti-ulcer activity have the general formula (I): (wherein R¹ is a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms; R² is a hydrogen atom or a methyl group; and R³ is a 3-butenyl group, a 4-pentenyl group or a 5-methyl-4-hexenyl group), or are pharmaceutic­ ally acceptable salts thereof.

Description: This invention relates to carbacyclin derivatives, and in particular to carbacyclin derivatives with anti-ulcer action. The invention also provides compositions containing these derivatives and processes for preparing them. Carbacyclin derivatives share in common the carbacyclin structure which is of the formula (A): Carbacyclin and its derivatives are chemically stable and have various physiological effects, including inhibition of blood platelet aggregation (GB Patent Specification 2012265A, US Patent 4238414). Compounds such as those of formula (B) below are now being developed as therapeutic agents for the treatment of thrombosis. More generally, the literature, such as GB Patent Specification 2012265A, US Patent 4238414 and US Patent 4338457, discloses that compounds of the formula (B), wherein the group R is an alkenyl group, have a variety of actions, including inhibition of blood platelet aggregation, anti-ulcer activity, inhibition of gastric juice secretion, and bronchodilatory activity. GB-A-2013661 and EP-A-11591 both disclose a very broad range of compounds having anti-ulcer activity, including some having the usual carbacyclin substituents, and wherein the 2-side-chain is selected from a large group having 0, 1 or 2 unsaturated positions, while Chem. Abs. 22363t discloses compounds saturated at the 2,3 or 3,4 positions, but not at the 1-position in the 2-substituent, and the carbacyclin ring is not fully saturated, where the 7-substituent is. The present invention provides carbacyclin derivatives with pharmacologically useful activity, especially anti-ulcer action. The carbacyclin derivatives of this invention are compounds of the general formula (I): (wherein R¹ represents a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms; R² represents a hydrogen atom or a methyl group; and R³ represents a 3-butenyl group, a 4-pentenyl group or a 5-methyl-4-hexenyl group). The carbacyclin derivatives of this invention further include the pharmaceutically acceptable salts of the compounds of formula (I). The present invention further embraces pharmaceutical compositions of the carbacyclin derivatives of the invention, particularly in view of their potent anti-ulcer activity. The anti-ulcer activity of the carbacyclin derivatives of this invention is particularly remarkable when compared with that of the structurally similar compounds which are disclosed in the state of the art and which are of the formula (B) given above wherein the group R is 2-pentenyl, 2,6-dimethyl-5-heptenyl, or the like. It is to be noted that the compounds of general formula (I) wherein the group R² is methyl also weakly exhibit other physiological effects shown by known carbacyclin derivatives, such as inhibition of blood platelet aggregation. Examples of alkyl groups which may be represented by R¹ include the methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl and decyl groups, with the methyl group being particularly preferred. Preferred compounds of formula (I) include those compounds wherein R¹ is a hydrogen atom or a methyl group, and R² and R³ as are defined above. Other preferred compounds of formula (I) include those compounds wherein R² is a methyl group, and R¹ and R³ are as defined above. Also preferred compounds of formula (I) include those compounds wherein R³ is a 3-butenyl or 4-pentenyl group, especially a 4-pentenyl group, and R¹ and R² are as defined above. Especially preferred compounds are those compounds wherein R² is a methyl group, and those compounds wherein R³ is a 3-butenyl or 4-pentenyl group, more particularly a 4-pentenyl group. Examples of the pharmacologically acceptable salts of this invention include the alkali metal and alkaline earth metal salts, such as the sodium, potassium, magnesium or calcium salts; the ammmonium salt; quaternary ammonium salts, such as the tetramethylammonium, tetraethylammonium, benzyltrimethylammonium or phenyltriethylammonium salts; salts with an aliphatic, alicyclic or araliphatic amine, such as the salts with methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, N -methylhexylamine, cyclopentylamine, dicyclohexylamine, benzylamine, α-phenylethylamine or ethylenediamine; salts with a heterocyclic amine or alkylheterocyclic amine, such as the salts with piperidine, morpholine, pyrrolidine, piperazine, pyridine, 1-methylpiperazine or 4-ethylmorpholine; and salts with an amine substituted with a hydrophilic radical, such as the salts with monoethanolamine, ethyldiethanolamine or 2-amino-1-butanol. If desired, a carbacyclin derivative of this invention can be used in the form of a clathrate compound with a host compound such as α-, β- or γ-cyclodextrin. The carbacyclin derivatives of this invention exist as optical isomers, due to the presence of asymmetric carbon atoms. The carbacyclin derivatives of formula (I) also exist as geometrical isomers, due to the double bonds. The preferred isomers have the steric configuration of carbacyclin itself and are of the following formula (Ia): (wherein R¹, R² and R³ as previously defined). Examples of preferred carbacyclin derivatives of this invention are the compounds of formula (I), and their salts. where R¹, R² and R³ are as defined in the following table: Especially preferred carbacyclin derivatives of this invention are Compounds No. 3, 5, 7 and 8 listed above. The listed carbacyclin derivatives preferably take the form of the isomer which is in agreement with the general formula (Ia) given above. Thus, the particularly preferred carbacyclin derivatives of this invention are: 16,16-dimethyl-19,20-didehydrocarbacyclin, and pharmaceutically acceptable salts thereof; 16-methyl-20-methylenecarbacyclin, and pharmaceutically acceptable salts thereof; 16,16-dimethyl-20-methylenecarbacyclin, and pharmaceutically acceptable salts thereof; and 16,16-dimethyl-20-methylenecarbacyclin methyl ester. The carbacyclin derivatives of the present invention have low toxicity and typically possess a good anti-ulcer activity. The effectiveness of the compounds of this invention is particularly noteworthy in comparison with existing prostacyclins. Effect on aspirin-induced ulcer According to a method reported by Brodie and Chase [Gastroenterology 53 , 600 (1967)], the anti-ulcer effect was determined. Five male rats of the Donryu strain (body weight 170 to 200 g) were used for each of the control and test compound groups. After being fasted for 24 hours, the rats were orally given certain concentrations of the test compounds (as shown in the following table); 15 minutes later, they were given orally 100 mg/kg of aspirin (Sanko Pharmaceutical Inc). Four hours after the administration of aspirin, the stomach was extracted and expanded with 10 ml of 0.5% formalin. An ulcer index was calculated from the total area of ulceration for the rats of the treated and control groups. The inhibition rate was calculated by comparing the ulcer indices of both groups. The following table shows the inhibition rate (%) for each concentration of the test compounds from 10γ/kg to 300γ/kg (where γ is 10⁻⁶ g). The reference compounds were as follows: Reference Compound A : Carbacyclin Reference Compound B : 17,18-Didehydrocarbacyclin Reference Compound C : 20-Isopropylidenecarbacyclin Reference Compound D : 17-Methyl-20-isopropylidenecarbacyclin The results show that the carbacyclin derivatives of the present invention have, at a concentration of 30 γ/kg, an inhibition rate around 3 times higher than the rate of the other, reference compounds. It is apparent that the carbacyclin derivatives of the present invention have useful anti-ulcer activity. Toxicity Testing When the compound of Preparative Example 1 was intravenously administered to five rats at 10 mg per kg of body weight per rat, no deaths occurred. This favourable acute toxicity test indicates that the toxicity of the compounds of this invention is very low. Thus, the compounds of the general formula (I) and pharmacologically acceptable salts thereof are of pharmaceutical use, especially for the therapeutic and preventive treatment of ulcers. The present invention accordingly provides pharmaceutical compositions comprising a carbacyclin derivative of general formula (I) or a pharmaceutically acceptable salt thereof, together with a pharmaceutically acceptable carrier or diluent. The compounds of the invention may be formulated as conventional pharmaceutical formulations, the nature of which will depend on the preferred route of administration. For example, for oral administration, preferred formulations include tablets, capsules, granules, powders and syrups. Non-oral administration may be, for example, by intravenous injection. The daily dose may vary depending on the symptoms, age and body weight of the patient, as well as the nature and severity of the disorder to be treated. Usually from about 0.001 mg to about 1000 mg, preferably from about 0.01 mg to about 100 mg, is administered per day for an adult, in a single dose or in divided doses. The carbacyclin derivatives of this invention can be prepared by adaption of existing methods, for example by adaption of the method described in GB Patent Specification 2012265. Thus, the compounds of the general formula (I) of this invention may be made by the steps shown in the following reaction scheme: In this reaction scheme, R¹, R² and R³ are as defined above, R⁴ and R⁵ are the same or different and each represents a hydroxy-protecting group, and Z represents a carbonyl-protecting group. Examples of hydroxy-protecting groups which may be represented by R⁴ and R⁵ include, for instance: heterocyclic groups, such as the tetrahydropyranyl or 4-methoxytetrahydropyran-4-yl groups; substituted methyl groups, such as the methoxymethyl or benzyloxymethyl groups; and silyl groups, such as the dimethyl-t-butylsilyl group. Examples of carbonyl-protecting groups which may be represented by Z include, for instance, groups giving acetal formation, with Z either being a single divalent group or two monovalent groups. Thus, examples of carbonyl-protecting groups for Z include: alkylenedioxy or alkylenedithio groups having from 1 to 4 carbon atoms, such as the ethylenedioxy or ethylenedithio groups: and gem-dialkoxy groups (where each alkoxy group has from 1 to 4 carbon atoms) such as the gem-dimethoxy or gem-diethoxy groups. The first step in the reaction scheme involves preparing an enone compound having the general formula (III). To this end, a formyl compound having the general formula (II) can be reacted with an anion having the general formula (VII): (wherein R² and R³ are as defined above, R⁶ represents an alkyl group of 1 to 4 carbon atoms, and M represents an alkali metal). The anion of formula (VII) can easily be obtained from a compound of general formula (VI): (where R², R³ and R⁶ are as defined above) by reaction with a base (for example, an alkali metal compound such as sodium hydride or n-butyllithium). The reaction with the base is typically effected at around room temperature for from 1 to 3 hours. The second step in the reaction scheme involves preparing a ketone compound having the general formula (IV). This step can be achieved by reducing the unprotected carbonyl group of the compound (III) and removing the protecting group Z from the other, remaining carbonyl group. The reduction of the unprotected carbonyl group gives an alcohol, which is itself conveniently protected with the group R⁵ after removal of the carbonyl-protecting group Z. If desired, the protecting group R⁴ employed in the compound (III) can be removed as part of this second step, and then reprotection effected when introducing the protecting group R⁵. The reduction of the carbonyl group can be carried out, for example, by reacting the compound (III) with a reducing agent (for instance, a metal hydride compound such as sodium borohydride, sodium borocyanohydride or lithium trimethoxyaluminohydride) in an inert solvent (for example, an alcohol such as methanol) at from 0°C to room temperature for from 30 minutes to 3 hours. The conditions for removing the carbonyl-protecting group Z vary depending on the nature of the protecting group to be removed. If the protecting group is a gem-dialkoxy or alkylenedioxy group, it can be removed by treating the compound with a mixture of an acid and an aqueous solvent, such as acetic acid-water, dilute hydrochloric acid-aqueous acetone, dilute hydrochloric acid-aqueous acetonitrile, dilute sulphuric acid-aqueous acetone or boron trifluoride etherate-aqueous acetone. If the protecting group is an alkylenedithio group, it can be removed by treating the compound with a suitable mercury reagent, such as mercuric chloride or mercuric oxide, in an inert solvent (for example, an ether such as dioxane, tetrahydrofuran or diethyl ether). The removal of the group Z is conveniently carried out at around room temperature for from 1 to 15 hours. The conditions for introducing the hydroxy-protecting group R⁵ will also vary depending on the nature of the protecting group. If the desired protecting group is a heterocyclic group, reaction can be carried out by treatment with a heterocyclic compound, such as dihydropyran or 4-methoxydihydropyran, in the presence of an acid (for example, hydrochloric acid, trifluoroacetic acid or p -toluenesulphonic acid) typically at from 0°C to room temperature for from 1 to 3 hours in an inert solvent (for example, a halogenated hydrocarbon such as methylene chloride). If the desired protecting group is a silyl group, reaction can be carried out by treatment with a corresponding halide in the presence of an organic amine (for example, pyridine, imidazole or triethylamine) typically around room temperature for from 1 to 3 hours in an inert solvent (for example, an aromatic hydrocarbon such as benzene). The third step in the reaction scheme involves preparing a carbacyclin compound having the general formula (V). It can be carried out by treating the compound (IV) with a Wittig reagent of the general formula (VIII): (where R¹ is as defined above and R⁷ represents an alkyl group having from 1 to 4 carbon atoms or an aryl group such as a phenyl group). The reaction with the Wittig reagent is suitably effected in an inert solvent (for example, an ether such as tetrahydrofuran, an aromatic hydrocarbon such as toluene, or a sulphoxide such as dimethyl sulphoxide), preferably in a stream of an inert gas such as nitrogen or argon. The Wittig reagent of general formula (VIII) can itself be prepared by treating a compound of the general formula (IX): (where R¹ and R⁷ are as defined above, and X represents a halogen atom such as chlorine or bromine) with a base, for example, an alkali metal hydride such as sodium hydride, an alkali metal alkoxide such as sodium ethoxide or potassium t-butoxide, or an alkali metal dimethylsulphoxide anion such as sodium dimethylsulphoxide ("dimsyl") anion, typically around room temperature for from 1 to 24 hours. The fourth step in the reaction scheme involves preparing a desired carbacyclin compound having the general formula (I). This step can be achieved by removing the hydroxy-protecting groups R⁴ and R⁵ from the compound (V). The conditions for the removal depend on the nature of the protecting group to be removed. If the protecting group is a heterocyclic or substituted methyl group, removal can be achieved by treatment with an acid (for example, an organic acid such as acetic acid, trifluoroacetic acid, p -toluenesulphonic acid or camphorsulphonic acid; or a mineral acid such as hydrochloric acid or sulphuric acid) in an inert solvent (for example, aqueous acetone or aqueous tetrahydrofuran) typically at from room temperature to 100°C for from 30 minutes to 5 hours. If the protecting group is a silyl group, removal can be carried out in water by treatment with an acid (for example, an organic acid such as acetic acid or trifluoroacetic acid; or a mineral acid such as hydrochloric acid or sulphuric acid), with a base (for example, an alkali such as sodium hydroxide or potassium carbonate) or with tetrabutylammonium fluoride, typically around room temperature for from 30 minutes to 3 hours. A silyl group can be also removed by treatment with an ammonium salt such as tetrabutylammonium fluoride in an inert solvent (for example, an ether). A compound of general formula (I) wherein R¹ is a hydrogen atom may then readily be converted to give a pharmacologically acceptable salt, for example by conventional salification. A compound of the general formula (I) in which R¹ is a hydrogen atom can be converted into a compound (I) in which R¹ is an alkyl group by conventional esterification. Esterification may be performed for example with a diazoalkane such as diazomethane, diazoethane or diazopropane, or with an alcohol-mineral acid such as methanol-hydrochloric acid, ethanol-hydrochloric acid or pentanol-hydrochloric acid. Correspondingly, a compound (I) in which R¹ is an alkyl group can be converted into a compound (I) in which R¹ is a hydrogen atom by conventional hydrolysis. Hydrolysis may be performed, for example, by reaction with an alkali metal hydroxide in an aqueous solvent, such as sodium hydroxide-aqueous methanol. A compound in which R¹ is an alkyl group can, if desired, be converted into a compound in which R¹ is another alkyl group by conventional ester exchange. Ester exchange may be performed, for example, by reaction with an alcohol in the presence of a base such as potassium carbonate. At the completion of each step in the reaction scheme the respective product can be isolated from the reaction mixture by conventional means. For example, after completion of a reaction step, the reaction mixture may, if appropriate, be neutralized or acidified, and then extracted with a suitable organic solvent. Such an extract can be washed and dried, and the product obtained by distilling off the solvent. The product at each step can if necessary be purified by conventional means such as column chromatography, thin layer chromatography and/or recrystallization. Where the product is obtained as a mixture of geometric and/or optical isomers, the isomers can be separated and resolved at any suitable step of the reaction scheme. The present invention is illustrated by the following non-limiting examples. Preparative Example 1 16-Methyl-20-methylenecarbacyclin (a) 2β-(3-Oxo-4-methylnona-1,8-dienyl)-3α-(2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo[3.3.0]-octane 482 mg of sodium hydride (a 55% dispersion in mineral oil) was washed with hexane and mixed with 100 ml of anhydrous tetrahydrofuran. The resultant suspension was cooled on an ice bath, 3.12 g of dimethyl 2-oxo-3-methyl-7-octenylphosphonate were added, and the mixture was stirred for 40 minutes. The solution was ice-cooled and 2.69 g of 2β-formyl-3α-(2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo[3.3.0]octane dissolved in 15 ml of tetrahydrofuran were mixed therewith and stirred for 2 hours. At the end of this time, 100 ml of a saturated aqueous sodium chloride solution were added, and the mixture was extracted with ethyl acetate. The extract was washed with a saturated aqueous sodium chloride solution and dried over anhydrous sodium sulphate. Evaporation of the solvent gave 4.57 g of a residue, which was purified by column chromatography using 90 g of alumina. The fraction eluted with hexane containing from 1 to 9% by volume ethyl acetate gave 3,08 g of the title compound as an oil. infrared absorption spectrum (liquid) ν max cm⁻¹: 1020, 1120, 1626, 1668, 1692 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 1.07 (3H, doublet); 3.89 (4H, singlet); 4.8-6.0 (3H, multiplet); 6.0-7.1 (2H, multiplet). (b) 2β-(3-Hydroxy-4-methylnona-1,8-dienyl)-3α-(2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo-[3.3.0]octane 3.05 g of the enone compound prepared as described in Preparative Example 1(a) dissolved in 23 ml of methanol were added to 3.26 g of cerium chloride heptahydrate dissolved in 25 ml of methanol at from 0° to 5°C. 470 mg of sodium borohydride were then added at from 0° to 3°C to the reaction solution, whilst stirring, and the mixture stirred for a further 30 minutes at the same temperature. At the end of this time, water was added and the system was extracted with ethyl acetate. The extract was washed with a saturated aqueous solution of sodium chloride and dried over anhydrous sodium sulfate. After distilling off the solvent, 3.01 g of the title compound were obtained as an oil. infrared absorption spectrum (liquid) ν max cm⁻¹: 1020, 1120, 1640, 3475 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.89 (3H, multiplet); 3.88 (4H, singlet); 4.67 (1H, broad singlet); 4.8-6.3 (5H, multiplet). (c) 2β-(3α-Hydroxy-4-methylnona-1,8-dienyl)-3α-hydroxy-7-oxo- cis -bicyclo[3.3.0]octane and 2β-(3β-hydroxy-4-methylnona-1,8-dienyl)-3α-hydroxy-7-oxo- cis -bicyclo[3.3.0]octane 2.97 g of the hydroxy compound prepared as described in Preparative Example 1(b) were dissolved in 6 ml of tetrahydrofuran, and 6.1 ml of acetic acid and 11 ml of water were added to the solution. The resultant mixture was then stirred at from 45° to 50°C for 2.5 hours. During this stirring, 20 ml of water divided into 8 aliquots were added. After cooling of the reaction solution, a 20% w/v aqueous sodium hydroxide solution was added to give neutrality, further saturated aqueous sodium chloride solution was added, and the system was extracted with ethyl acetate. The organic layer was washed with a saturated aqueous sodium chloride solution and dried over anhydrous sodium sulphate. Evaporation of the solvent gave 2.61 g of a residue, which was purified by column chromatography using 78 g of silica gel. The fraction eluted with hexane containing from 38 to 44% by volume ethyl acetate gave 591 mg of the 2β-(3β-hydroxy) compound as an oil; the fraction eluted with hexane containing from 44 to 54% by volume ethyl acetate gave 279 mg of a mixture of the 2β-(3α-hydroxy) and 2β-(3β-hydroxy) compounds; and the fraction eluted with hexane containing from 54 to 95% by volume ethyl acetate gave 937 mg of the 2β-(3α-hydroxy) compound as an oil. 2 β -(3α-hydroxy) compound: infrared absorption spectrum (liquid) ν max cm⁻¹: 1640, 1738, 3400 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.86 (3H, multiplet); 3.95 (2H, broad), 4.80-6.20 (5H, multiplet). 2β-(3β-hydroxy) compound infrared absorption spectrum (liquid) ν max cm⁻¹: 1640, 1730, 3400 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.90 (3H, doublet); 3.95 (2H, broad), 4.8-6.2 (5H, multiplet). (d) 2β-[3α-(2-Tetrahydropyranyloxy)-4-methylnona-1,8-dienyl]-3α-(2-tetrahydropyranyloxy)-7-oxo- cis -bicyclo[3.3.0]octane 900 mg of the 2β-(3α-hydroxy) compound prepared as described in Preparative Example 1(c) were dissolved in 15 ml of methylene chloride. The solution was added to 0.85 ml of dihydropyran. While cooling the solution with ice, 10 mg of p -toluenesulphonic acid were added and the mixture was stirred for 100 minutes. A saturated aqueous sodium bicarbonate solution was added, followed by a saturated aqueous sodium chloride solution, and the system was extracted with ethyl acetate. The organic extract was washed with a saturated aqueous sodium chloride solution and dried over anhydrous sodium sulphate. After distilling off the solvent, 1.49 g of the crude title compound was obtained as an oil. infrared absorption spectrum (liquid) ν max cm⁻¹: 1020, 1030, 1130, 1640, 1740 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.86 (3H, multiplet); 4.70 (2H, broad singlet); 5.9-6.2 (5H, multiplet). (e) 16-Methyl-20-methylenecarbacyclin 11,15-ditetrahydropyranyl ether and its 5Z-isomer Dimsyl sodium, which had been previously prepared from 1.25 g of sodium hydride (55% dispersion in mineral oil) and 80 ml of dimethyl sulphoxide, was dissolved in dimethyl sulphoxide. Under a stream of nitrogen, 8.65 g of triphenyl 4-carboxybutylphosphonium bromide were added. After stirring the mixture for 20 minutes, 25 ml of dimethyl sulphoxide containing 1.46 g of the ketone compound prepared as described in Preparative Example 1(d) was added, and the mixture was allowed to stand overnight. At the end of this time, 30 ml of ice water, 50 ml of cyclohexane and 1.0 ml of concentrated hydrochloric acid were added in this order and the layers were separated. The aqueous layer was extracted with cyclohexane, and the combined organic layers were washed with a saturated aqueous sodium chloride solution, and then dried over anhydrous sodium sulphate. After distilling off the solvent, 2.62 g of the resulting residue was purified by column chromatography using 40 g of silica gel. The fraction eluted with hexane containing from 13 to 15% by volume ethyl acetate gave 345 mg of the 5Z-isomer; then the fraction eluted with hexane containing from 15 to 19% by volume ethyl acetate gave 107 mg of a mixture of the 5Z-isomer and the 5E-isomer; and finally the fraction eluted with hexane containing from 20 to 55% by volume ethyl acetate gave 804 mg of the 5E-isomer as an oil. 5Z-Isomer infrared absorption spectrum (liquid) ν max cm⁻¹: 973, 1640, 1708, 1740 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.90 (3H, multiplet); 4.60-6.20 (8H, multiplet). 5E-Isomer infrared absorption spectrum (liquid) ν max cm⁻¹: 974, 1020, 1640, 1708, 1736 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.90 (3H, multiplet): 4.60-6.20 (8H, multiplet). (f) 16-Methyl-20-methylenecarbacyclin 10 ml of water and 40 mg of camphorsulphonic acid were added to 23 ml of acetone containing 750 mg of the 5E-isomer of the dipyranyl compound prepared as described in Preparative Example 1(e). The resultant solution was heated and stirred at about 60°C for 90 minutes. At the end of this time, 25 ml of water was added and the system was extracted with ethyl acetate. The extract was washed with water and dried over anhydrous sodium sulphate. After distilling off the solvent, the resulting residue was purified by column chromatography using 13 g of silica gel. The fractions eluted with hexane containing 40% by volume ethyl acetate and subsequently with ethyl acetate gave 338 mg of the title compound as an oil. infrared absorption spectrum (liquid) ν max cm⁻¹: 1640, 1708, 3340 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.86 (3H, multiplet); 3.3-4.1 (2H, broad); 4.8-6.2 (6H, multiplet). A corresponding methyl ester was obtained by esterification of this compound with diazomethane. infrared absorption spectrum (liquid) ν max cm⁻¹: 970, 1640, 1735, 3370 Preparative Example 2 16-Methyl-19,20-didehydrocarbacyclin (a) 2β-(3-Oxo-4-methylocta-1,7-dienyl)-3α-(2-tetra-hydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo[3.3.0]-octane From 439 mg of sodium hydride (55% dispersion in mineral oil), 2.95 g of dimethyl 2-oxo-3-methyl-6-octenylphosphonate and 2.60 g of 2β-formyl-3α-(2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo-[3.3.0]octane. 3.23 g of the title compound was obtained as an oil by similar reaction and treatment to those described in Preparative Example 1(a). infrared absorption spectrum (liquid) ν max cm⁻¹: 1030, 1120, 1622, 1668, 1694 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 1.10 (3H, doublet); 3.92 (4H, singlet); 4.68 (1H, multiplet); 4.8 -7.2 (5H, multiplet). (b) 2β-(3-Hydroxy-4-methylocta-1,7-dienyl)-3α-(2-tetrahydropyranyloxy)-7,7-ethelenedioxy- cis -bicyclo-[3.3.0]octane From 3.53 g of cerium chloride heptahydrate, 507 mg of sodium borohydride and 3.19 g of the enone compound prepared in Preparative Example 2(a), 3.15 g of the title compound were obtained as an oil by similar reaction and treatment to those described in Preparative Example 1(b). infrared absorption spectrum (liquid) ν max cm⁻¹: 1020, 1120, 1640, 3480 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.90 (3H, multiplet); 4.70 (1H, broad); 4.80-6.2 (5N, multiplet). (c) 2β-(3α-Hydroxy-4-methylocta-1,7-dienyl)-3α-hydroxy-7-oxo- cis -bicyclo[3.3.0]octane and 2β-(3β-hydroxy-4-methylocta-1,7-dienyl)-3α-hydroxy-7-oxo- cis -bicyclo[3.3.0]octane From 3.12 g of the hydroxy compound prepared in Preparative Example 2(b) and 6.6 ml of acetic acid, 970 mg of oily 2β-(3α-hydroxy) compound and 535 mg of oily 2β-(3β-hydroxy) compound were obtained by similar reaction and treatment to those described in Preparative Example 1(c). 2β-(3α-hydroxy) compound infrared absorption spectrum (liquid) ν max cm⁻¹: 1640, 1738, 3400 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.89 (3H, multiplet); 4.8-6.2 (5H, multiplet). 2β-(3β-hydroxy) compound infrared absorption spectrum (liquid) ν max cm⁻¹: 1640, 1730, 3400 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.88 (3H, doublet); 4.8 -6.2 (5H, multiplet). (d) 2β-[3α-(2-Tetrahydropyranyloxy)-4-methylocta-1,7-dienyl]-3α-(2-tetrahydropyranyloxy)-7-oxo- cis -bicyclo[3.3.0]octane From 900 mg of the 2β-(3a-hydroxy) compound prepared in Preparative Example 2(c) and 0.89 ml of dihydropyran, 1.51 g of the crude title compound was obtained as an oil by similar reaction and treatment to those described in Preparative Example 1(d). infrared absorption spectrum (liquid) ν max cm⁻¹: 970, 1020, 1032, 1130, 1640, 1740 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.90 (3H, multiplet); 4.5-6.2 (7H, multiplet). (e) 16-Methyl-19,20-didehydrocarbacyclin-11,15-ditetrahydropyranyl ether From 1.39 g of sodium hydride (55% dispersion in mineral oil), 64 ml of dimethyl sulphoxide, 9.35 g of triphenyl-4-carboxybutylphosphonium bromide and 1.58 g of the ketone compound prepared in Preparative Example 2(d), 695 mg of the title compound as an oil and 370 mg of its 5Z-isomer were obtained by similar reaction and treatment to those described in Preparative Example 1(e). 5E-Isomer infrared absorption spectrum (liquid) ν max cm⁻¹: 1020, 1640, 1708, 1738 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.90 (3H, multiplet); 4.5-6.2 (8H, multiplet). 5Z-Isomer infrared absorption spectrum (liquid) ν max cm⁻¹: 1020, 1640, 1710, 1740 (f) 16-Methyl-19,20-didehydrocarbacyclin From 665 mg of the dipyranyl 5E-isomer prepared in Preparative Example 2(e), 345 mg of the title compound was obtained as an oil by similar reaction and treatment to those described in Preparative Example 1(f). infrared absorption spectrum (liquid) ν max cm⁻¹: 970, 1640, 1708, 3350 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.88 (3H, multiplet); 3.3-4.1 (2H, broad); 4.8-62. (6H, multiplet). Preparative Example 3 16,16-Dimethyl-20-methylenecarbacyclin (a) 2β-(3-Oxo-4,4-dimethylnona-1,8-dienyl)-3α-(2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo-[3.3.0]octane From 440 mg of sodium hydride (55% dispersion in mineral oil), 3.30 g of dimethyl 2-oxo-3,3-dimethyl-7-octenyl phosphonate and 2.50 g of 2β-formyl-3α-(2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo-[3.3.0]octane, 3.09 g of the title compound was obtained as an oil by similar reaction and treatment to those described in Preparative Example 1(a). infrared absorption spectrum (liquid) ν max cm⁻¹: 985, 1030, 1625, 1691 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 1.12 (6H, singlet); 3.90 (4H, singlet); 4.5-4.8 (1H, multiplet); 4.8-6.1 (3H, multiplet); 6.4-7.1 (2H, multiplet). (b) 2β-(3-Hydroxy-4,4-dimethylnona-1,8-dienyl)-3α-(2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo[3.3.0]octane From 2.66 g of cerium chloride heptahydrate, 350 mg of sodium borohydride and 3.07 g of the enone compound prepared in Preparative Example 3(a), 3.03 g of the title compound were obtained as an oil by similar reaction and treatment to those described in Preparative Example 1(b). infrared absorption spectrum (liquid) ν max cm⁻¹: 975, 1022, 1641, 3490 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.85 (3H, singlet); 0.89 (3H, singlet); 3.91 (4H, singlet); 4.70 (1H, broad), 4.8-6.1 (5H, multiplet). (c) 2β-(3α-Hydroxy-4,4-dimethylnona-1,8-dienyl)-3α-hydroxy-7-oxo- cis -bicyclo[3.3.0]octane and 2β-(3β-hydroxy-4,4-dimethylnona-1,7-dienyl)-3α-hydroxy-7-oxo- cis -bicyclo[3.3.0]octane From 3.03 g of the hydroxy compound prepared in Preparative Example 3(b) and 30 ml of acetic acid, 1.31 g of oily 2β-(3α-hydroxy) compound and 760 mg of oily 2β-(3β-hydroxy) compound were obtained by similar reaction and treatment to those described in Preparative Example 1(c). 2β-(3α-hydroxy) compound infrared absorption spectrum (liquid) ν max cm⁻¹: 975, 1642, 1740, 3420 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.85 (3H, singlet); 0.89 (3H, singlet); 3.7-4.1 (2H, multiplet); 4.8-6.2 (5H, multiplet). 2β-(3β-hydroxy) compound infrared absorption spectrum (liquid) ν max cm⁻¹: 974, 1641, 1740, 3420 (d) 2β-[3α-(2-Tetrahydropyranyloxy)-4,4-dimethylnona-1,8-dienyl]-3α-(2-tetrahydropyranyloxy)-7-oxo- cis -bicyclo[3.3.0]octane From 1.29 g of the 2β-(3α-hydroxy) compound prepared in Preparative Example 3(c) and 1.15 ml of dihydropyran, 1.98 g of the crude title compound was obtained as an oil by similar reaction and treatment to those described in Preparative Example 1(d). infrared absorption spectrum (liquid) ν max cm⁻¹: 1022, 1034, 1642, 1742 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.7-1.0 (6H, multiplet); 4.68 (2H, broad), 4.8-6.2 (5H, multiplet). (e) 16,16-Dimethyl-20-methylenecarbacyclin-11,15-ditetrahydropyranyl ether From 1.63 g of sodium hydride (55% dispersion in mineral oil), 100 ml of dimethyl sulphoxide, 10.12 g of triphenyl 4-carboxybutylphosphonium bromide and 1.97 g of the ketone compound prepared in Preparative Example 3(d), 1.06 g of the title compound as an oil and 0.6 g of its 5Z-isomer were obtained by similar reaction and treatment to those described in Preparative Example 1 (e). 5E-Isomer infrared absorption spectrum (liquid) ν max cm⁻¹: 980, 1645, 1714, 1741 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.7-1.0 (6N, multiplet); 4.6-6.2 (8H, multiplet). 5Z-Isomer infrared absorption spectrum (liquid) ν max cm⁻¹: 980, 1645, 1714, 1741 (f) 16,16-Dimethyl-20-methylenecarbacyclin 1.05 g of the 5E-isomer of the dipyranyl compound prepared in Preparative Example 3(e) was dissolved in 21 ml of acetic acid. To this solution was added 5 ml of water, and the mixture was stirred at room temperature. After 30 minutes and again after 1 hour, 2.5 ml of water was added and the reaction solution was stirred for a further 14 hours. At the end of this time, 50 ml of a 20% w/v aqueous sodium hydroxide solution was added, followed by a saturated aqueous sodium chloride solution, and the system was extracted with ethyl acetate. The extract was washed with a saturated solution of sodium chloride and dried over anhydrous sodium sulphate. After distilling off the solvent, the resulting residue was purified by silica gel column chromatography to give 0.56 g of the title compound as an oil. infrared absorption spectrum (liquid) ν max cm⁻¹: 970, 1640, 1710, 3380 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.86 (3H, singlet); 0.90 (3H, singlet); 3.4-4.0 (2H, multiplet); 4.8-6.2 (6H, multiplet). The title compound was esterified with diazomethane to afford the corresponding methyl ester. infrared absorption spectrum (liq) ν max cm⁻¹: 973, 1438, 1642, 1742, 3400 Preparative Example 4 16,16-Dimethyl-19,20-didehydrocarbacyclin (a) 2β-(3-Oxo-4-methylocta-1,7-dienyl)-3α-(2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo[3.3.0]-octane From 430 mg of sodium hydride (55% dispersion in mineral oil), 2.90 g of dimethyl 2-oxo-3,3-dimethyl-6-heptenylphosphonate and 2.60 g of 2β-formyl-3α-(2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo-[3.3.0]octane, 3.20 g of the title compound were obtained as an oil by similar reaction and treatment to those described in Preparative Example 1(a). infrared absorption spectrum (liquid) ν max cm⁻¹: 985, 1030, 1625, 1690 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 1.12 (6H, singlet); 3.94 (4H, singlet); 4.5-4.8 (1H, multiplet); 4.8-6.1 (3H, multiplet); 6.4-7.1 (2H, multiplet). (b) 2β-(3-Hydroxy-4,4-dimethylocta-1,7-dienyl)-3α-(2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo[3.3.0]octane From 3.52 g of cerium chloride heptahydrate, 508 mg of sodium borohydride and 3.09 g of the enone compound prepared in Preparative Example 4(a), 3.05 g of the title compound were obtained as an oil by similar reaction and treatment to those described in Preparative Example 1(b). infrared absorption spectrum (liquid) ν max cm⁻¹: 974, 1020, 1641, 3490 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.84 (3H, singlet); 0.89 (3H, singlet); 3.91 (4H, singlet); 4.70 (1H, broad); 4.1-4.8 (5H, multiplet). (c) 2β-(3α-Hydroxy-4,4-dimethylocta-1,7-dienyl)-3α-hydroxy-7-oxo- cis -bicyclo[3.3.0]octane and 2β-(3β-hydroxy-4,4-dimethylocta-1,7-dienyl)-3α-hydroxy-7-oxo- cis -bicyclo[3.3.0]octane From 3.02 g of the hydroxy compound prepared in Preparative Example 4(b) and 6.6 ml of acetic acid, 1.33 g of the 2β-(3α-hydroxy) compound and 759 mg of the 2β-(3β-hydroxy) compound were obtained, both as oils, by similar reaction and treatment to those described in Preparative Example 1(c). 2β-(3α-hydroxy) compound infrared absorption spectrum (liquid) ν max cm⁻¹: 975, 1641, 1740, 3421 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.84 (3H, singlet); 0.89 (3H, singlet); 3.7-4.1 (2H, multiplet); 4.8-6.2 (5H, multiplet). 2β-(3β-hydroxy) compound infrared absorption spectrum (liquid) ν max cm⁻¹: 974, 1641, 1740, 3420 (d) 2β-[3α-(2-Tetrahydropyranyloxy)-4,4-dimethylocta-1.7-dienyl]-3α-(2-tetrahydropyranyloxy)-7-oxo- cis -bicyclo[3.3.0]octane From 880 mg of the 2β-(3α-hydroxy) compound prepared in Preparative Example 4(c) and 0.86 ml of dihydropyran, 1.32 g of the crude title compound was obtained as an oil by similar reaction and treatment to those described in Preparative Example 1(d). infrared absorption spectrum (liquid) ν max cm⁻¹: 1022, 1034, 1642, 1741 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.7-1.0 (6H, multiplet); 4.67 (2H, broad.), 4.8-6.2 (5H, multiplet). (e) 16,16-Dimethyl-19,20-didehydrocarbacyclin-11,15-ditetrahydropyranyl ether From 1.39 g of sodium hydride (55% dispersion in mineral oil), 60 ml of dimethyl sulphoxide, 9.39 g of triphenyl-4-carboxybutylphosphonium bromide and 1.31 g of the ketone compound prepared in Preparative Example 4(d), 659 mg of the title compound as an oil and 341 mg of its 5Z-isomer were obtained by similar reaction and treatment to those described in Preparative Example 1(e). 5E-Isomer infrared absorption spectrum (liquid) ν max cm⁻¹: 980, 1604, 1713, 1741 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.7-1.0 (6H, multiplet); 4.6-6.2 (8H, multiplet). 5Z-Isomer infrared absorption spectrum (liquid) ν max cm⁻¹: 980, 1644, 1713, 1741 (f) 16,16-Dimethyl-19,20-didehydrocarbacyclin From 630 mg of the 5E-isomer of the dipyranyl compound prepared in Preparative Example 4(e), 314 mg of the title compound was obtained as an oil by similar reaction and treatment to those described in Preparative Example 3(f). infrared absorption spectrum (liquid) ν max cm⁻¹: 972, 1640, 1710, 3380 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.86 (3H, singlet); 0.90 (3H, singlet): 3.4-4.0 (2H, multiplet); 4.8-6.2 (6H, multiplet). Preparative Example 5 16-Methyl-20-methylenecarbacyclin decyl ester 200 mg of the methyl ester compound prepared in Preparative Example 1(f) were dissolved in 2 ml of decyl alcohol. 100 mg of potassium carbonate were added and the mixture was stirred for 2 hours at 100°C. After cooling the reaction solution, an aqueous sodium chloride solution was added, and the system was extracted with ethyl acetate. The extract was washed with an aqueous sodium chloride solution and dried over anhydrous sodium sulphate. After distilling off the solvent, the residue was purified by silica gel column chromatography. The fraction eluted with hexane containing from 30 to 50% by volume ethyl acetate gave 209 mg of the title compound as an oil. infrared absorption spectrum (liquid) ν max cm⁻¹: 965, 1170, 1378, 1450, 1640, 1735 Preparative example 6 16-Methyl-20-isopropylidenecarbacyclin (a) 2β-(3-Oxo-4,9-dimethyldeca-1,8-dienyl)-3α-(2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -bicyclo[3.3.0]octane. The same procedures as described in the above Preparative Example 1(a) were followed, except that there were employed 483 mg of sodium hydride (55% dispersion in mineral oil), 3.48 g of dimethyl 2-oxo-3,8-dimethyl-7-nonenylphosphonate and 2.69 of 2β-formyl-3α-(2-tetrahydropynanyloxy)-7,7-ethylenedioxy- cis -bicyclo[3.3.0]octane, giving 3.36 g of the title product as an oily substance. infrared absorption spectrum (liquid) ν max cm⁻¹: 1030, 1120, 1622, 1665, 1692. nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 1.10 (3H, singlet); 1.58 (3H, singlet); 1.67 (3H, singlet): 4.68 (1H, multiplet); 4.87 (4H, singlet); 5.10 (1H, multiplet); 6.0-6.9 (2H, multiplet). (b) 2β-(3-Hydroxy-4,9-dimethyldeca-1,8-dienyl)-3α-2-tetrahydropyranyloxy)-7,7-ethylenedioxy- cis -biyclo-[3.3.0)octane The same procedures were followed as described in the above Preparative Example 1(b), except that there were employed 3.35 g of cerium chloride heptahydrate, 485 mg of sodium borohydride and 3.34 g of the enone prepared in Preparative Example 6(a), giving 3.34 g of the title product as an oily substance. infrared absorption spectrum (liquid) ν max cm⁻¹: 1020, 1120, 3475 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.90 (3H, multiplet); 3.88 (1H, broad); 4.67 (1H, broad); 5.15 (1H, multiplet); 5.58 (2H, multiplet). (c) 2β-(3α-hydroxy-4,9-dimethyldeca-1,8-dienyl)-3α-hydroxy-7-oxo- cis -bicyclo[3.3.0]octane Following the same procedure as described in the above Preparative Example 1(c) except that 3.29 g of the hydroxy compound prepared in Preparative Example 6(b) and 8.3 ml of acetic acid were used, there were obtained 950 mg of the title product as an oily substance. infrared absorption spectrum (liquid) ν max cm⁻¹: 1738, 3400 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.93 (3H, multiplet); 1.60 (3H, singlet); 1.68 (3H, singlet); 5.12 (1H, multiplet); 5.46 (2H, multiplet). (d) 2β-[3α-(2-Tetrahydropyranyloxy)-4,9-dimethyldeca-1,8-dienyl]-3α-(2-tetrahydropyranyloxy)-7-oxo- cis -bicyclo[3.3.0]octane Following the same procedures as described in the above Preparative Example 1(d) except that 910 mg of the 2β-(3α-hydroxy) compound prepared in Preparative Example 6(c) and 0.8 ml of dihydropyran were used, there were obtained 1.50 g of the crude title product as an oily substance. infrared absorption spectrum (liquid) ν max cm⁻¹: 966,1018,1032,1740 (e) 16-Methyl-20-isopropylidenecarbacyclin-11,15-ditetrahydropyranyl ether Following the same procedure as described in the above Preparative Example 1(e) except that 1.45 g of sodium hydride (55% dispersion in mineral oil), 64 ml of dimethyl sulphoxide, 9.3 g of triphenyl-4-carboxybutylphosphonium bromide and 1.47 g of the ketone prepared as described in the Preparative Example 6(d) were used, there were obtained 570 mg of the title product as an oily substance and 334 mg of its 5Z isomer. 5E isomer: infrared absorption spectrum (liquid) ν max cm⁻¹: 1020, 1710, 1740 5Z Isomer infrared absorption spectrum (liquid) ν max cm⁻¹: 1020, 1710, 1740 (f) 16-Methyl-20-isopropylidenecarbacyclin Following the same procedure as described in the above Preparative Example 1(f), except that there were employed 540 mg of the dipyranyl compound prepared as described in the Preparative Example 6(e), there were obtained 223 mg of the title product as an oily substance. infrared absorption spectrum (liquid) ν max cm⁻¹: 970, 1704, 3350 nuclear magnetic resonance spectrum (CDCℓ₃) δppm: 0.88 (3H, multiplet); 1.60 (3H, singlet); 1.69 (3H, singlet); 3.80 (2H,broad); 4.9-5.6 (4H, multiplet). An example of a pharmaceutical composition of this invention is now given. Pharmaceutical composition Capsules 20 mg of the compound of Preparative Example 1 were dissolved in 20 g of ethanol, and the solution was well mixed with 100 g of lactose. Ethanol was distilled off under reduced pressure, and the resulting lactose mixture was used to fill 100 mg-hard capsules (containing the active ingredient at around 0.02%) to give capsule preparations. If necessary, a little lubricant such as magnesium stearate may be employed.

Claims: A compound of general formula (I): (wherein R¹ is a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms; R² is a hydrogen atom or a methyl group; and R³ is a 3-butenyl group, a 4-pentenyl group or a 5-methyl-4-hexenyl group), and pharmaceutically acceptable salts thereof. A compound according to claim 1, wherein R¹ is a hydrogen atom or a methyl group. A compound according to claim 1 or claim 2, wherein R² is a methyl group. A compound according to any one of claims 1 to 3, wherein R³ is a 3-butenyl group or a 4-pentenyl group. A compound according to any one of claims 1 to 3, wherein R³ is a 4-pentenyl group. A compound according to claim 1 or claim 2, wherein R¹ is as defined, R² is a methyl group, and R³ is a 3-butenyl group or a 4-pentenyl group. A compound according to claim 6, wherein R³ is a 4-pentenyl group. A compound according to any one of the preceding claims, which is a compound of the formula (Ia): (wherein R¹, R² and R³ are as previously defined), or a pharmaceutically acceptable salt thereof. 16,16-Dimethyl-19,20-didehydrocarbacyclin and pharmaceutically acceptable salts thereof. 16-Methyl-20-methylenecarbacyclin and pharmaceutically acceptable salts thereof, 16,16-Dimethyl-20-methylenecarbacyclin and pharmaceutically acceptable salts thereof. 16,16-Dimethyl-20-methylenecarbacyclin methyl ester. A pharmaceutical composition comprising an anti-ulcer compound, together with a pharmaceutically acceptable carrier or diluent, said anti-ulcer compound being a compound as claimed in any one of claims 1 to 12. The use in the manufacture of a medicament for the treatment of ulcers of a compound as claimed in any one of claims 1 to 12. Claims for the following Contracting State: AT A process for preparing a compound of formula (I'): (in which: R¹ represents a hydrogen atom or a C₁-C₁₀ alkyl group: R² represents a hydrogen atom or a methyl group; R³ represents a 3-butenyl group, a 4-pentenyl group or a 5-methyl-4-hexenyl group; and R⁴ ' and R⁵ ' each represent a hydrogen atom or a hydroxy-protecting group) or a pharmaceutically acceptable salt thereof, which process comprises reacting a compound of formula (IV'): (in which R², R³, R⁴′ and R⁵′ are as defined above) with a Wittig reagent of formula (VIII): (in which R¹ is as defined above and R⁷ represents a C₁-C₄ alkyl group or an aryl group), optionally remvoing hydroxy-protecting groups and optionally salifying the product. A process according to claim 1, in which R⁴ ' and R⁵ ' in said compound of formula (IV') both represent hydroxy-protecting groups and these are removed after reaction with said Wittig reagent. A process according to claim 1 or claim 2, wherein R¹ is a hydrogen atom or a methyl group. A process according to any one of claims 1 to 3, wherein R² is a methyl group. A process according to any one of claims 1 to 4, wherein R³ is a 3-butenyl group or a 4-pentenyl group. A process according to claim 5, wherein R³ is a 4-pentenyl group. A process according to any one of the preceding claims, wherein the compound of formula (I') which is prepared has the stereochemistry shown by the following formula (Ia): (wherein R¹, R² and R³ are as previously defined). A process according to claim 1 or claim 2, wherein the starting materials and reaction conditions are so selected as to prepare: 16,16-dimethyl-19,20-didehydrocarbacyclin, 16-methyl-20-methylenecarbacyclin, 16,16-dimethyl-20-methylenecarbacyclin, 16,16-dimethyl-20-methylenecarbacyclin methyl ester, or a pharmaceutically acceptable salt of any of these compounds. The use in the manufacture of a medicament for the treatment of ulcers and other therapeutic purposes of a compound of formula (I): (where R¹, R² and R³ are as defined in any one of claims 1 and 3-6) or a pharmaceutically acceptable salt thereof.

Inventors: KOBAYASHI, SHINSAKU, KOJIMA, KOICHI
Applicants: SANKYO COMPANY LIMITED
Application year: 1986
Main classification: C07C59
IPC codes: C07C69, C07C59, A61K31, C07C405, A61P1, C07H15