SUBSTITUTED 2,3,4,9-TETRAHYDRO-1H-CARBAZOLE-1-ACETIC ACID DERIVATIVES

Abstract: Substituted 2,3,4,9-tetrahydro-1H-carbazole-1-acetic acid derivatives and methods for their preparation and use are disclosed. The compounds are useful analgesic and anti-inflammatory agents. The derivatives are acids of formula I below or their salts. In formula (I) R¹, R², R³, R⁴, R⁵ and R⁶ are hydrogen or lower alkyl or R³ and R⁴ are joined together to form (CH₂) m or R⁵ and R⁶ are joined together to form -CH=CH-CH=CH-, (CH₂) n , -CH=CH=O- or -CH=CH-S-, R⁸ and R¹⁰ are independently hydrogen, lower alkyl or halogen, R⁹ is hydrogen or lower alkyl, m is 2 to 3 and n is 2 to 4.

Description: This invention relates to tricyclic acetic acid derivatives, to their preparation and use, and to inter­ mediates used for their preparation. More specifically, this invention relates to tricyclic acetic acid derivatives in which the tricyclic portion thereof is characterized by having an indole portion fused to a cyclohexane ring. Still more specifically, the compounds of this invention are characterized as derivatives of the following tricyclic acetic acid system: 2,3,4,9-tetrahydro-1H-carbazole-1-acetic acid which is substituted at the 4- position and optionally further substituted at other positions, e.g. the 1-, 7- and 8-­ positions. The tricyclic acetic acid compounds of this invention possess useful pharmacologic properties; for instance, they exhibit analgesic and anti-inflammatory activity at dose levels which do not elicit undesirable side effects. The foregoing combination of attributes renders the compounds of this invention useful for the treatment of inflammatory conditions and of pain. Prior Art. The closest prior art to the present invention is Asselin et al. United States Patent No. 4,057,559. Asselin discloses analgesic and anti-­ inflammatory agents having the same heterocyclic ring system as the present invention but without the substituents of the present invention. Demerson et al. United States Patent No. 3,939,178 discloses 1,3,4,9-­ tetrahydropyrano[3,4-b]indoles and 1,3,4,9-tetrahydrothiopyrano[3,4-b]indoles having analgesic and antiinflammatory activity. Related United State Patents are Nos. 3,974,179 and 3,843,681. Boehringer Mannheim European Patent 42593 generically discloses starting materials useful for producing cardiotonic and beta-blocking agents. The starting materials include 1,2,3,4-tetrahydrocarbazoles with substituents selected from the broad group including hydrogen, carboxy, lower alkyl and lower alkenyl. The starting materials are in each case also substituted with a reactive group which distinguishes them from the compounds of the present invention. Further removed, related patents that include tetrahydrocarbazoleacetic acid derivatives useful as analgesic and antiinflammatory agents are United States Patents 4,234,487; 4,264,500; 4,193,923; 4,158,007 4,146,542; 3,896,145 and 3,824,314; Japanese Patent J51032556; Netherland Patent NL 7,100,213 and Great Britain Patent GB 1385620. The novel compounds of this invention are represented by formula (I) wherein R¹, R², R³, R⁴, R⁵ and R⁶ are hydrogen or lower alkyl or R³ and R⁴ may be joined together to form (CH₂) m or R⁵ and R⁶ may be joined together to form -CH=CH-CH=CH-, (CH₂) n , -CH=CH-O- or -CH=CH-S-, R⁸ and R¹⁰ are independently hydrogen, lower alkyl or halogen, R⁹ is hydrogen or lower alkyl, m is 2 to 3, and n is 2 to 4 and the pharmaceutically acceptable salts thereof. A preferred aspect of the present invention are the compounds represented by formula (II). wherein R¹, R², R³, R⁴, R⁵, and R⁶ are independently hydrogen or lower alkyl containing 1 to 6 carbon atoms or R³ and R⁴ may be joined together to form (CH₂)₃ or R⁵ and R⁶ may be joined together to form -CH=CH-CH=CH-, (CH₂)₄, -CH=CH-O- or -CH=CH-S-, R⁸ and R¹⁰ are independently hydrogen, lower alkyl containing 1 to 6 carbon atoms or halogen, R⁹ is hydrogen or lower alkyl containing 1 to 6 carbon atoms, and the pharmaceutically acceptable salts thereof. A still further preferred aspect of the present invention are the compounds represented by formula (III) wherein R⁴, R⁵ and R⁶ are hydrogen or R⁵ and R⁶ may be joined together to form -CH=CH-CH=CH-, R⁸ and R¹⁰ are independently hydrogen, methyl, ethyl or chlorine and the pharmaceutically acceptable salts thereof. The most preferred compounds of the present invention are designated cis-1,8-diethyl-2,3,4,9-tetrahydro-4-(2-­ propenyl)-1H-carbazole-1-acetic acid, cis-1-ethyl-2,3,4,9-­ tetrahydro-4-(2-propenyl)-1H-carbazole-1-acetic acid, 1,8-diethyl-2,3,4,9-tetrahydro-4(phenylmethyl)-1H-carbazole-­ 1-acetic acid, cis-7,8-dichloro-1-ethyl-2,3,4,9-tetrahydro-­ 4-(2-propenyl)-1H-carbazole-1-acetic acid, cis-7-chloro-1-­ ethyl-2,3,4,9-tetrahydro-8-methyl-4-(2-propenyl)-1H-­ carbazole-1-acetic acid, and cis-1-ethyl-2,3,4,9-tetrahydro-­ 8-methyl-4-(2-propenyl)-1H-carbazole-1-acetic acid and the pharmaceutically acceptable salts thereof. The compounds of the present invention may be prepared by a process in which an ester of structure wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁸, R⁹ and R¹⁰ are as defined above and R⁷ is lower alkyl, is hydrolysed. The ester may be prepared by treating a hydrazone of structure (VII) wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as defined above, with a cyclizing agent. The hydrazone may be prepared by a process in which an unsaturated ketone of structure (IV) wherein R¹ is as defined above and R⁷ is lower alkyl is reacted with an organometallic reagent wherein R², R³, R⁴, R⁵ and R⁶ are as defined above and M may be SiMe₃ as described by H. Sakurai in Pure Apple Chem., 54 , 1 (1982), or SnBu₃, in both cases carrying out the reaction in the presence of an acid such as titanium tetrachloride, or M may be MgBr, MgCl or Mgl, carrying out the reaction in the presence of a suitable copper catalyst selected from the group consisting of copper bromide dimethyl sulfide complex, cuprous iodide, cuprous bromide, copper acetate, cuprous chloride and tributylphosphine cuprous iodide complex, to obtain a compound or compounds of structures Va, Vb, Vc or Vd. wherein R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are as defined above and further reacting a compound of structure (V) with a substituted hydrazine of formula (VI) wherein R⁸ and R¹⁰ are independently hydrogen, lower alkyl or halogen and R⁹ is hydrogen or lower alkyl to obtain the corresponding hydrazine of structure (VII). The compounds of the invention may also be prepared by cyclizing a hydrazone corresponding to that of structure (VII) above in which R⁷ is hydrogen. The hydrazone may be prepared in an analogous manner to that of structure (VII) from a starting material of structure (V) in which R⁷ is hydrogen. The term "lower alkyl" as used herein contemplates straight chain alkyl radicals containing from one to six carbon atoms and branched chain alkyl radicals containing from three to four carbon atoms and includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl and the like. The term "halogen" as used herein includes fluorine, chlorine, bromine and iodine. The compounds of formula (I) form salts with suitable pharmaceutically acceptable inorganic and organic bases. These derived salts possess similar activity to the parent acid and are included within the scope of this invention. The acid of formula (I) may be transformed in excellent yield into the corresponding pharmaceutically acceptable salts by neutralization of said acid with the appropriate inorganic or organic base. The salts are administered in the same manner as the parent acid compounds. Suitable inorganic bases to form these salts include, for example, the hydroxides, carbonates, bicarbonates or alkoxides of the alkali metals or alkaline earth metals, for example, sodium, potassium, magnesium, calcium and the like. Suitable organic bases include the following amines; lower mono-, di- and tri-alkylamines, the alkyl radicals of which contain up to three carbon atoms, such as methylamine, dimethylamine, trimethylamine, ethylamine, di- and triethylamine, methylethylamine, and the like; mono- di- and trialkanolamines, the alkanol radicals of which contain up to three carbon atoms, such as mono-, di- and triethanolamine; alkylenediamines which contain up to six carbon atoms, such as hexamethylenediamine; phenyl substituted alkylamines, such as benzenemethanamine; cyclic saturated or unsaturated bases containing up to six carbon atoms, such as pyrrolidine, piperidine, morpholine, piperazine and their N-alkyl and N-hydroxyalkyl derivatives, such as N-methylmorpholine and N-(2-hydroxyethyl)piperidine, as well as pyridine. Furthermore, there may be mentioned the corresponding quaternary salts, such as the tetraalkyl (for example tetramethyl), alkyl-alkanol (for example, methyltrimethanol and trimethyl-monoethanol) and cyclic ammonium salts, for example the N-methyl­ pyridinium, N-methyl-N-(2-hydroxyethyl)-morpholinium, N,N-dimethyl­ morpholinium, N-methyl-N-(2-hydroxyethyl)-morpholinium, N,N-­ dimethylpiperidinium salts, which are characterized by good water-solubility. In principle, however, there can be used all the ammonium salts which are physiologically compatible. The transformations to the salts can be carried out by a variety of methods known in the art. For example, in the case of the inorganic salts, it is preferred to dissolve the acid of formula (I) in water containing at least one equivalent amount of a hydroxide, carbonate, or bicarbonate corresponding to the inorganic salt desired. Advantageously, the reaction is performed in a water-miscible organic solvent inert to the reaction conditions, for example, methanol, ethanol, dioxane, and the like in the presence of water. For example, such use of sodium hydroxide, sodium carbonate or sodium bicarbonate gives a solution of the sodium salt. Evaporation of the solution or addition of a water-miscible solvent of a more moderate polarity, for example, a lower alkanol, for instance, butanol, or a lower alkanone, for instance, ethyl methyl ketone, gives the solid inorganic salt if that form is desired. To produce an amine salt, the acid of formula (I) is dissolved in a suitable solvent of either moderate or low polarity, for example, ethanol, acetone, ethyl acetate, diethyl ether and benzene. At least an equivalent amount of the amine corresponding to the desired cation is then added to that solution. If the resulting salt does not precipitate, it can usually be obtained in solid form by addition of a miscible diluent of low polarity, for example, benzene or petroleum ether, or by evaporation. If the amine is relatively volatile, any excess can easily be removed by evaporation. It is preferred to use substantially equivalent amounts of the less volatile amines. Salts wherein the cation is quaternary ammonium are produced by mixing the acid of formula (I) with an equivalent amount of the corresponding quaternary ammonium hydroxide in water solution, followed by evaporation of the water. Included in the present invention are the diastereo isomers wherein the 4-­ substituent is either cis or trans to the acetic acid chain at position one. Also included in this invention are the optical isomers of the compounds of formula (I) which result from asymmetric centers, contained therein. Such isomers are obtained in substantially pure form by classical separation techniques and by sterically controlled synthesis. Antiinflammatory Activity The useful antiinflammatory activities of the tricyclic acetic acid derivatives of formula (I) and their salts are demonstrated in standard pharmacologic tests, for example, the test designated: PREVENTATIVE ADJUVANT EDEMA. The objective of this test is to determine the ability of test drugs to exhibit an acute anti-inflammatory effect in rats. This test is a primary screen for anti-inflammatory drugs. Species: Male Sprague Dawley rats (180-200g) are used. The animals have free access to water but food is withdrawn 18 hours before testing. Drug Preparations and Administration: Freund's complete adjuvant is prepared by suspending 5 mg killed and dried Mycobacterium butyricum (Difco) in 1 ml liquid paraffin. The test compounds are dissolved in distilled water or suspended in distilled water with a few drops of Tween 80 according to their solubility. For primary screening all drugs are administered by gastric lavage at the arbitrary dosage of 100 mg/kg, p.o. in a volume of 0.5 ml/100 g body weight to groups of 10 animals. Methodological Details: The method is essentially that described by Wax et al. , J. Pharmacol. Exp. Ther., 192 , 166-171 (1975). Groups of rats are injected intradermally in the left hind paw with 0.1 ml of Freund's complete adjuvant. The test compound or vehicle is administered immediately before the adjuvant, 24 hours and 48 hours after the adjuvant (day 0,1 and 2). The injected hind paw volume is measured before the injection of adjuvant and 24 hrs. after the last drug administration (day 3) by means of plethysmometer (Buxco Electronics Inc.). The difference between the hind paw volume on day 0 and day 3 represents the edema volume. Phenylbutazone (50 mg/kg, p.o.) is included as a positive control. Presentation of Results: The mean edema volume (expressed as ml ± SEM) is calculated for each group and the percentage protection conferred by the drug is calculated: where c is the mean edema volume for the untreated controls and t is the mean edema volume for the drug treated group. A further test used to determine the utility of the compounds of the present invention is designated: DRUG EFFECTS ON PHENYLQUINONE-­ INDUCED WRITHING IN MICE The objective of this test is to determine the ability of test drugs to inhibit the nociceptive (pain) response of mice injected with a chemical irritant. This test is a primary screen for both peripheral and centrally acting analgesic drugs. Species: Male Swiss albino mice (15-25g). The animal are fasted for 18 hours prior to use but have free access to water. Drug Preparation and Administration: Drugs are dissolved or suspended according to their solubility in 0.5% methyl cellulose or 0.5% Tween 80. They are administered by gastric lavage in a volume of 5 ml/kg. For primary screening all drugs are administered at the arbitary dosage of 200 mg/kg, p.o. to a group of 10 mice. Methodological Details: A modification of the method of Siegmund et al. , Proc. Soc. Exp. Biol. Med., 95 , 729-731 (1957) is used. Groups of 5 mice are dosed with the test compound or vehicle control. Sixty minutes later the animals are injected i.p. with 0.3 ml/20 g body weight of a 0.02% solution of phenylquinone (PBQ; 2-phenyl-1,4-benzoquinone) and placed in individual observation boxes. The number of writhing or abdominal squirming movements made by each mouse during the following 15 min. period is counted. The experiment is repeated with another group of 5 mice and the mean number of writhes per mouse for a group of 10 mice is calculated. Presentation of Results: Drug treated and vehicle-treated control groups are compared and the percentage protection conferred by the drug is calculated: where c = mean number of writhes in the control group where t = mean number of writhes in the test drug group A still further test used to determine the utility of the compounds of the present invention is designated: PAW PRESSURE TEST IN THE RAT The objective of this test is to assess the potency of peripheral and central acting drugs in inhibiting the reaction of rats to painful stimulation applied to an inflamed paw. Species: Male Sprague Dawley rats (180-200g) are used. The animals are fasted overnight prior to drug administration. Drug Preparation and Administration: Freund's Complete Adjuvant (FCA) is prepared by suspending 5 mg killed and dried mycobacterium butyricum (Difco) in 1 ml liquid paraffin. The test compounds are dissolved, or suspended with a few drops of Tween 80, in distilled water according to their solubility. They are administered by gastric gavage in a volume of 0.5 ml/100 g of body weight to groups of 10 animals. Methodological Details: Ten rats are used per group. The method is essentially that described by Randall, et al., Arch. Int. Pharmacodyn. 111 , 409 (1957) and the apparatus which is used to apply pressure to the paw (Analgesy-meter for the rat paw, Ugo Basile from Coulbourn Instruments) is a modification of that described by Gilfoil et al ., J. Pharmacol. 142 , 1 (1963). The instrument is basically a device which exerts a force that increases at a constant rate. The force is continuously monitored by a pointer moving along a linear scale and is measured in grams. The inflammatory reaction is induced in the left hind paw of rats by injecting 0.1 ml of Freund's adjuvant intradermally. The test compound or vehicle is administered 24 hours after the adjuvant. Prior to drug administration the rats are selected for their paw sensitivity. Rats responding to a pain threshold greater than 10 g applied to the inflamed paw are rejected. The pain threshold (vocalization) is determined 1 and 3 hours later in the inflamed paw and the normal paw of the treated and control groups. The higher of the 2 readings will be considered as representative of the drug effect on the pain threshold. Presentation of results and Criteria for Activity: Each animal which has a reading 1.5 times greater than the mean reading of the control-group will be considered as responsive to treatment. The number of animals showing an analgesic effect is then determined in each group. The ED₅₀ (dose which causes analgesia in 50% of the animals) using at least 3 doses is then determined, by the method described in Litchfield et al., J. Pharmacol. Exp. Ther., 96 , 99 (1949). Typical results obtained for the compounds of the present invention in the aforementioned tests are as follows: The lack of side effects for the compounds of this invention are demonstrated by standard acute toxicity tests described by R.A. Turner in "Screening Methods in Pharmacology," Academic Press, New York and London, 1965, pp. 152-163 and by prolonged administration of the compound to warm-­ blooded animals. When the compounds of this invention are employed as antiinflammatory and analgesic agents in warm-blooded animals, they are administered orally, alone or in dosage forms, i.e., capsules or tablets, combined with pharmacologically acceptable excipients, such as starch, milk sugar and so forth, or they are administered orally in the form of solutions in suitable vehicles such as vegetable oils or water. The compounds of this invention may be administered orally in sustained release dosage form or transdermally in ointments or patches. The compounds of this invention may also be administered in the form of suppositories. The dosage of the compounds of formula I of this invention will vary with the particular compound chosen and form of administration. Furthermore, it will vary with the particular host under treatment. Generally, the compounds of this invention are administered at a concentration level that affords protective effects without any deleterious side effects. These antiinflammatory effective concentration levels are usually obtained within a therapeutic range of 1.0 µg to 500 mg/kg per day, with a preferred range of 10 µg to 100 mg/kg per day. The compounds of this invention also possess antipyretic activity. The compounds of this invention may be administered together with the usual doses of caffeine. The preferred process for obtaining the compounds of the present invention is exemplified by the process for obtaining 4-substituted-1,8-diethyl-2,3,4,9-­ tetrahydro-1H-carbazole-1-acetic acids (XII) outlined in Scheme 1. In Scheme 1, Step 1, 2-ethylcyclohexanone (VIII) was alkylated with methyl bromoacetate according to the procedure of E. Negishi et al. Tet. Lett. 24 , 1341 (1983) in the presence of potassium hydride, and triethylborane in tetrahydrofuran. This afforded 2-carbomethoxymethyl-2-ethylcyclohexanone (IX) in 45% yield. Compound (IX) was previously reported in Asselin et al., J. Med. Chem., 19 , 787 (1976). About 5-10% of the 2,6 regioisomer was also formed which was separated by flash chromatography. Conversion of (IX) to 2-phenylseleno-6-carbomethoxymethyl-6-­ ethylcylcohexanone with phenylselenenylchloride according to the procedure of K.B. Sharpless et al., J. Amer. Chem. Soc. 95 , 6137 (1973) and oxidative elimination with hydrogen peroxide in Step 2 led to the required enone (X) in 55-­ 68% yield in a one pot conversion. Conjugate addition of organometallic reagents RM to (X) in Step 3 wherein R is PhCH₂- or CH₂=CH-CH₂-and M is MgCl or SiMe₃ gave trisubstituted ketone (XI) as a mixture of diastereomers. Fischer indole cyclization with 2-­ ethylphenylhydrazine in Step 4 and subsequent base hydrolysis in Step 5 gave tetrahydrocarbazoles (XII). The diastereomers, which represent another aspect of the invention, can be separated either before or after cyclization. Conjugate addition reactions of organometallic reagents RM to (X) in Step 3 gave a 1:1 to a 1.5:1 mixture of diastereomers when carried out. at -40°C in tetrahydrofuran (THF) by adding an ether or THF solution of the Grignard reagent (1 to 1.4 equivalents) to a solution of (X) in THF/Me₂S containing 0.1 equivalents of copper bromide dimethyl sulfide complex [(K.J. Shea et al. Tetrahedron Lett., 24 , 1003 (1983)]. See Table 1, Entry 1. When allyltrimethylsilane was added to (X) in the presence of titanium tetrachloride [(H. Sakurai, Pure Appl., Chem., 54 , 1 (1982)] a 13:1 mixture of diastereomers as evidenced by capillary GC, analytical HPLC and 200MHz NMR was obtained. The major diastereomer was cis. The ketones (XI) were then subjected to Fischer indole synthesis conditions in Step 4 by refluxing with 2-ethylphenylhydrazine in methanol the appropriate time to form the hydrazone (See Table 2). The hydrazone solution was then cooled to 0°C, treated with acetyl chloride to generate HCl and refluxed an additional 45 minutes to affect Fischer indole cyclization. The esters were then hydrolyzed in Step 5 with potassium carbonate in aqueous methanol to afford tetrahydro-1-H-carbazole-1-acetic acids (XII). Compounds of formula (I) where R⁹= lower alkyl can also be prepared by treating an ester of compound (I), where R⁹= H, with sodium hydride or potassium hydride in a suitable solvent followed by treatment with an alkyl halide followed by hydrolysis of the ester. The requisite starting materials of formula (VI), phenylhydrazine or substituted phenylhydrazines are known or may be prepared according to known methods. A convenient method for preparing the substituted phenylhydrazines involves the diazotization of the appropriately substituted aniline to give the corresponding diazo derivative. The latter compound is then reduced with stannous chloride or sodium sulfite to give the corresponding phenylhydrazine, see L. F. Fieser and M. Fieser, "Advanced Organic Chemistry," Reinhold Publishing Corporation, New York, 1961, p. 734. The requisite starting materials of formula (IX) may be prepared by several methods. At least three of these methods are illustrated in Asselin et al., United States Patent No. 4,057,559. The above starting materials of formula (V) and formula (VI) may be used to prepare the compounds of this invention in the following manner: The starting material of formula (VI) may be condensed with substantially one molar equivalent of the starting material of formula (V) to give the corresponding hydrazone of formula (VII) in which R¹ to R⁹ inclusive and m and n are as defined hereinbefore. Generally speaking, the condensation is performed preferably in an inert atmosphere, for example, nitrogen or argon. The condensation can be carried out in the absence of a solvent, but if desired, a suitable solvent may be used eg. one selected from the group consisting of the lower alkanols such as methanol and ethanol; aromatics such as benzene and toluene; the ethers, such as tetrahydrofuran, diethyl ether, dioxane, bis(2-methoxyethyl)-ether and the like; and the halogenated hydrocarbons, methylene chloride, chloroform and the like. Methanol, ethanol and toluene are preferred solvents. Times and temperatures for the condensation generally range from 5 minutes to five or six days at 0° to 100°C. Convenient time and temperature ranges include 20°C to the boiling point of the mixture and 15 minutes to 130 hours. Preferably, the reaction is run without solvent. The resulting hydrazone (VII) may then be cyclized to the tricyclic ester of formula (I) by the action of a suitable cyclization agent according to the conditions of the "Fischer Indole Synthesis," for example, see B. Robinson, Chem. Rev. 63 , 373 (1963). A variety of cyclization agents are effective for this cyclization, some of the agents suitable for this cyclization include p-toluenesulfonic acid, hydrogen chloride or hydrogen chloride generated from acetyl chloride, hydrogen bromide, phosphoric acid, sulfuric acid, aluminum chloride, zinc chloride, hydrogen bromide in acetic acid, boron trifluoride-etherate, trifluoroacetic acid, cationic ion exchange resins such as Amberlite IR-120, phenyl or ethyl magnesium bromide and aniline salts. In other words the usual catalysts employed for the "Fischer Indole Synthesis" are efficacious; however, the preferred cyclization agent is a solution of boron trifluoride etherate in acetic acid. In practice the isolation of the hydrazone (VII) from the condensation reaction mixture is optional. Accordingly, the cyclization agent is added either to the above condensation reaction mixture containing the hydrazone, or to the isolated hydrazone optionally dissolved in one of the above solvents, whereby the hydrazone then cyclizes to give the corresponding tricyclic ester of formula (I) in which R¹ to R⁹ inclusive and m and n are as defined hereinbefore. The cyclization usually proceeds smoothly and rapidly. Convenient reaction times for the cyclization include five minutes to two hours, preferably 30 minutes to one hour. Convenient temperatures include 20° to 200°C, preferably 120° to 180°C. In practice a most convenient and practical procedure for effecting the above cyclization comprises evaporating solvent from the condensation reaction mixture containing the hydrazone if a solvent was used, and then heating the hydrazone at reflux in a solution of boron trifluoride etherate in acetic acid. The starting material of formula (V) may be either a cycloalkanoneacetic acid derivative or its corresponding lower alkyl ester (R⁷=lower alkyl). Accordingly, when the acid is employed, the above process yields the tricyclic compound identical to the desired compound of formula (I) and when the starting material is lower alkyl ester the above process yields the lower alkyl ester tricyclic compound of formula (I). The subsequent conversion of the lower alkyl ester tricyclic compound of formula (I) to the corresponding compound of formula (I) is effected readily by subjecting the tricyclic compound to hydrolysis. Generally speaking, this conversion is most conveniently performed by employing a base as the hydrolyzing agent. The hydrolysis is performed in the presence of sufficient water optionally under an inert atmosphere, followed by acidification of the reaction mixture to yield the desired compound of formula (I). However, the manner of hydrolysis is not intended to be limited to basic hydrolysis since hydrolysis under acidic conditions and other variations, for example, treatment with lithium iodide in collidine (see. L.F. Fieser and M. Fieser, "Reagents for Organic Synthesis," John Wiley and Sons, Inc., New York, 1967, (pp. 615-617) are also applicable. For basic hydrolysis a preferred embodiment involves subjecting the tricyclic ester to the action of a base, for example, sodium or potassium carbonate, in the presence of sufficient water to effect hydrolysis of the ester. The hydrolysis is performed using a suitable solvent, for example, methanol or ethanol under a nitrogen atmosphere. The reaction mixture is maintained at a temperature of from 25°C to the reflux temperature until hydrolysis occurs. Usually from 10 minutes to 48 hours is sufficient for this hydrolysis. The reaction mixture is then rendered acidic with an acid, for example, acetic acid, hydrochloric acid, sulfuric acid and the like, to release the free acid as a solid. Alternatively, the tricyclic ester is hydrolyzed by subjecting the ester to the action of a hydrolyzing agent which is a strong organic or inorganic acid, for example, trifluoroacetic acid, p-toluenesulfonic acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, phosphoric acid and the like in a suitable solvent at a temperature of at least 60°C and preferably from 90°C to the boiling point of the mixture until the hydrolysis occurs. Usually from 5 to 48 hours are required for this hydrolysis. Suitable solvents include water, acetic acid, aqueous alcohols and the like. If acid hyrolysis is used, the free acid is formed directly. If necessary, the reaction mixture can be diluted with water to precipitate the product. The following examples further illustrate this invention. EXAMPLE 1 cis-1,8-Diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-carbazole-1-acetic Acid (XII, R= -CH₂-CH=CH₂) a) Preparation of 2-Ethylcyclohexanone (VIII) 2-Ethylcyclohexanol (1.6 moles, 204 g, 226 ml) was stirred in 3.2 l of acetone at 0°C and treated with 8 N Jones reagent (prepared from 106.8 g of CrO₃ suspended in 92 ml of concentrated sulfuric acid and diluted to 400 ml with water) until the orange color persisted (∿430 ml). Isopropanol was then added to turn the solution green again after which it was poured into 2 l of ether. The product was washed with 6 x 500 ml of brine, dried over MgSO₄ and stripped of solvent. Short path distillation (b.p. 80-85°C at 25 mm) afforded 184 g (1.46 moles, 91%) of 2-ethylcyclohexanone as a colorless oil. b) Preparation of 1-Ethyl-2-oxocyclohexaneacetic Acid Methyl Ester (IX) According to the procedure of E. Negishi and S. Chatterjee, Tet. Lett., 24 , 1341 (1983), potassium hydride (417 mmol, 70 ml, ∿6M in mineral oil) was placed under nitrogen in a three-necked flask equipped with a mechanical stirrer and was washed three times with petroleum ether (this washing can be omitted). Tetrahydrofuran (200 ml, distilled from sodium/Ph₂CO) was then added followed by a solution of 2-ethylcyclohexanone (VIII) (50 g, 396 mmol) in 200 ml of tetrahydrofuran added as a slow stream over ∿15 minutes. The additon was followed one minute later by 495 ml of 1 M Et₃B in tetrahydrofuran followed 1 hour later by 594 mmol (91 g, 56 ml) of methyl bromoacetate. The yellow suspension was stirred for 2.5 hours, poured into 800 ml of water (being careful to decant away from excess KH!) and extracted with 4 x 300 ml of petroleum ether. The combined organic phases were dried over sodium sulfate and concentrated in vacuo . The product was distilled through a 6 inches Vigreux column collecting the material boiling at 107-118°C at 0.8 mm (the two regioisomers from the alkylation). This material was then purified by flash chromatography (4 inches diameter column, 7.5% ethyl acetate in petroleum ether eluent, 5 1/2 inches of silica gel) to afford 35.33 g (178.2 mmol, 45%) of colorless oil. The desired product is the lower R f material of the two overlapping spots on thin layer. R f =0.23 in 10% ethyl acetate/petroleum ether. About 5-10% of the 2,6 regioisomer can be isolated as the top spot. c) Preparation of 1-Ethyl-2-oxocyclohex-3-eneacetic Acid Methyl Ester (X) The ketone, 2-carbomethoxymethyl-2-ethylcyclohexanone (IX) (141 mmol, 28 g) was stirred in 1.25 l of ethyl acetate (dried over 3A molecular sieves) and treated with 169 mmol (32.5 g) of PhSeCl. The reaction was stirred under nitrogen for 4 hours then treated with 250 ml of water. The mixture was shaken vigorously in a separatory funnel and the organic phase was returned to the reaction flask. Tetrahydrofuran (550 ml) was then added followed by 35 ml of 30% H₂O₂ (aq.) added dropwise. The reaction mixture was stirred for one hour then washed with 500 ml of water and 500 ml of saturated Na₂CO₃ (aq.). The product was then dried over MgSO₄ and concentrated in vacuo . Flash chromatography (4 inches diameter column, 20% ethyl acetate in petroleum ether eluent, 5 1/2 inches of silica gel) afforded 15.3 g (78.0 mmol, 55%) of the product as a pale yellow oil. R f =0.9 in 15% ethyl acetate/petroleum ether on TLC. d) Preparation of cis-1-Ethyl-2-oxo-4-(2-propenyl)cyclohexaneacetic Acid Methyl Ester (XI, R=CH₂-CH=CH₂) The enone, 6-carbomethoxymethyl-6-ethyl-2-cyclohexen-1-one (X) 81.53 mmol, 16.0 g) was stirred in 82 ml of dry CH₂Cl₂ (distilled from CaH₂) at -78°C under nitrogen and treated dropwise with 122.30 mmol (23.2 g) of TiCl₄ followed by 97.84 mmol (11.18 g, 15.55 ml) of allyltrimethylsilane. After 1.5 hours, the reaction was quenched at -78°C with 50 ml of MeOH, poured into 200 ml of water and extracted with 4 x 100 ml of ether. Drying (Na₂SO₄) and flash chromatography (95 mm column, 15% EtOAc/petroleum ether eluent, 51/2 inches of silica gel) afforded 16.02 g (67.2 mmol, 82%) of colorless oil. The product appeared to be predominantly one diastereomer in at least a 9:1 ratio, the major diastereomer being cis. R f =0.39 in 15% ethyl acetate/petroleum ether on TLC. e) Preparation of cis-1,8-Diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-­ carbazole-1-acetic Acid Methyl Ester (XII, R=CH₂-CH=CH₂, methyl ester) The ketone, cis-1-ethyl-2-oxo-4-(2-propenyl)cyclohexaneacetic acid methyl ester (XI, R=CH₂-CH=CH₂) (51.14 mmol, 12.188 g) and the 2-­ ethylphenylhydrazine (51.14 mmol, 6.965 g) were refluxed in 219 ml of MeOH for 120 hours. The reaction was cooled to 0°C, treated with 102 mmol (8.0 g, 7.3 ml) of AcCl and refluxed for an additional 45 minutes. Solvent removal and flash chromatography (95 mm column, 12% EtOAc/petroleum ether eluent, 5 1/2 inches of silica gel) afforded 7.0 g (20.64 mmol, 40%) of orange oil. R f =0.54 in 15% ethyl acetate/petroleum ether on TLC. f) Preparation of cis-1,8-Diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-­ carbazole-1-acetic Acid (XII, R=CH₂-CH₂=CH₂) The ester, cis-1,8-diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-carbazole-1-­ acetic acid methyl ester (XII, R=CH₂-CH=CH₂, methyl ester)(20.64 mmol, 7.007 g) and K₂CO₃ (24.77 mmol, 3.423 g) were refluxed in 165 ml of MeOH containing 21 ml of water under nitrogen for 27.5 hours. Most of the MeOH was removed in vacuo and the residue was dissolved in 50 ml of water. The solution was acidified to pH ∿1 with 3 M HCl (aq.) and extracted with 4 x 50 ml of Et₂O. The combined organic solutions were dried over MgSO₄ and concentrated. Flash chromatography (75 mm column, 40% EtOAc/petroleum ether eluent, 5 1/2 inches of silica gel) afforded 5.0152 g (15.41 mmol, 75%) of yellow oil. Liquid chromatography showed that the product was predominately one isomer in at least a ∿9:1 ratio, the major diastereomer being cis. Three grams of the compound were recrystallized from 20 ml of 2:1 petroleum ether/benzene to afford 1.3 g of off-white needles (m.p. 121-124°C). A liquid chromatogram of the recrystallized material indicated 99.3% purity and a second crop was 97.6% pure. NMR(CDCl₃/TMS): 0.85(t,3H,J=8,CH₂C H ₃), 1.33(t,J=8,3H,ArCH₂C H ₃), 1.6-2.5 (m,6H,C H ₂CH₃, ring CH₂), 2.5-3.4(m,7H,CH,CH₂COO,ArC H ₂CH₃,C=CCH₂), 4.9-5.3(m,2H,C=CH₂), 5.6-6.3(m,1H,C H =CH₂), 7.0-7.6(m,3H, aromatics), 8.98(broad s,1H,NH). IR(KBr): 3600-3100(OH), 3400(NH), 1710(C=O). EXAMPLE 2 1,8-Diethyl-2,3,4,9-tetrahydro-4-(phenylmethyl)-1H-carbazole-1-acetic Acid (XII, R=phenylmethyl) a) Preparation of 1-Ethyl-2-oxo-4-(phenylmethyl)cylcohexaneacetic Acid Methyl Ester (XI, R=PhCH₂) The enone, 1-ethyl-2-oxocyclohex-3-eneacetic acid methyl ester (X), prepared by the process of Example 1, Step (c), (56.26 mmole, 11.04 g), Me₂S (11.25 ml) and 5.626 mmol (1.15 g) of CuBr·Me₂S were stirred in 165.5 ml of THF at - 40°C under nitrogen and treated with 56.26 mmol (28.1 ml of 2 M in THF) of PhCH₂MgCl added dropwise. The reaction was then quenched with 150 ml of 1M HCl and extracted with 4 x 100 ml of petroleum ether. The organic phases were dried over Na₂SO₄ and concentrated. Flash chromatography (95 mm column, 12% ethyl acetate/petroleum ether eluent) afforded 11.20 g (38.84 mmol, 69%) of yellow oil as a mixture of isomers. b) Preparation of 1,8-Diethyl-2,3,4,9-tetrahydro-4-(phenylmethyl)-1H-­ carbazole-1-acetic Acid Methyl Ester (XII, R=PhCH₂, methyl ester) The mixture of isomeric ketones prepared in Step (a), (74.56 mmol, 17.775 g) and the 2-ethylphenylhydrazine (74.56 mmol, 10.156 g) were refluxed in 320 ml of MeOH under nitrogen for 112 hours. The reaction was cooled to 0°C, treated with 112 mmol (8.78 g, 8 ml) of AcCl and refluxed an additional 45 minutes. The reaction was then concentrated in vacuo and flash chromatography (95 mm column, 12% EtOAc/petroleum ether eluent, 5 1/2 inches of silica gel) afforded 8.922 g (22.9 mmol, 31%) of yellow oil as a mixture of isomers. c) Preparation of 1,8-Diethyl-2,3,4,9-tetrahydro-4-(phenylmethyl)-1H-­ carbazole-1-acetic Acid (XII, R=PhCH₂) The isomeric esters obtained in Step (b), (22.9 mmol, 8.922 g) and K₂CO₃ (27.48 mmol, 3.798 g) were heated at reflux in 183 ml of MeOH and 23 ml of water under nitrogen for 26.5 hours. Most of the MeOH was removed in vacuo and the residue was dissolved in 50 ml of water. The solution was acidified to pH ∿1 with 3 M HCl (aq.), extracted with 4 x 50 ml of ether, dried over MgSO₄ and concentrated. Flash chromatography (75 mm column, 50% EtOAc/petroleum ether eluent, 5 1/2 inches of silica gel) afforded 6.7712 g (18.03 mmol, 79%) of yellow oil. About 1 g of each isomer was separated using reverse phase (C₁₈) chromatography and each was recrystallized from ∿2/1 petroleum ether/benzene as white crystals. Both isomers were dried in vacuo (72°C, silica gel desiccant) for 8 hours. The first isomer eluted by reverse phase chromatography (60/40 CH₃Cl/H₂O with 0.001 M KH₂PO₄) was designated the A isomer and had m.p. 185-186°C. The second eluted isomer was designated the B isomer and had m.p. 181-184°C. A isomer: NMR(CDCl₃/TMS): 0.9 (t, 3H, J=9, CH₂C H ₃), 1.36 (t,3H, J=9, ArCH₂C H ₃), 1.5-­ 2.3 (m, 7H, ring CH₂ and CH), 2.6-3.6 (m, 6H, PhCH₂, ArCH₂, CH₂COO), 7.0-7.6 (m, 8H, aromatics), 8.9 (broad s 1H, NH). IR (KBr): 3440(NH), 3600-3000(OH), 3060(CH aromatic), 3000-2880(CH aliphatic), 1710(C=O) B isomer: NMR (CDCl₃/TMS): 0.88 (t, J=9, 3H, CH₂C H ₃), 1.36 (t, J=9, 3H, ArCH₂C H ₃), 1.6-2.2 (m, 7H, ring CH₂ and CH), 2.7-3.5 (m, 6H, PhCH₂, ArCH₂, CH₂COO), 6.9-7.6 (m, 8H, aromatics), 9.0 (broad s, 1H, NH). IR (KBr): 3600-2500(OH), 3420(NH), 1700(C=O). EXAMPLE 3 cis-1-Ethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-carbazole-1-acetic Acid (III, R⁴, R⁵, R⁶, R⁸,R¹⁰=H) a) Preparation of cis-1-Ethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-­ carbazole-1-acetic Acid Methyl Ester Five grams (20.98 mmol) of cis-1-ethyl-2-oxo-4-(2-­ propenyl)cyclohexaneacetic acid methyl ester, prepared by the process of Example 1, Step (d), and 2.27 g (21 mmol, 2.07 ml) of 2-phenylhydrazine were heated at reflux under nitrogen in 21 ml of toluene with azeotropic removal of water. After 24 hours, the toluene was removed in vacuo and the residue was dissolved in 15 ml of acetic acid. It was treated with 27.27 mmol (3.87 g, 3.35 ml) of boron trifluoride etherate and refluxed under nitrogen for 20 minutes. The reaction mixture was poured into 40 ml of water and extracted with 4 x 40 ml of ether. The combined organic phases were washed with 2 x 20 ml of saturated sodium bicarbonate (aq.) and dried over magnesium sulfate. Flash chromatography (75 mm columm, 7% ethyl acetate in petroleum ether eluent, 5 1/2 inches of silica gel) afforded 3.04 g (9.81 mmol, 47%) of an orange oil. R f =0.65 in 15% EtOAc/petroleum ether. IR (neat): 3490(NH), 2850-3050(CH), 1715(C=O). NMR (CDCl₃/TMS, 200 MHz): 0.836(t, J=7.5, 3H, CH₂C H ₃), 1.258(t, J=7.15, 3H, ArCH₂C H ₃), 1.6-2.4, 2.6-2.8 (m, 8H, C H ₂CH₃, (CH₂CH₂C, C=CHC H ₂), 2.664 (5.2H, C H ₂COOMe), 3.05 (m, C=CHCH₂C H ), 3.703 (s, 3H, OCH₂), 5.0-5.1 (m, 2H, C=CH₂), 5.8-6.0 (m, 1H, H₂C=C H ), 7.0-7.6 (m, 4H, aromatics), 9.3 (broad s, 1H, NH). b) Preparation of cis-1-Ethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-­ carbazole-1-acetic Acid A solution of the ester, cis-1-ethyl-2,3,4,5-tetrahydro-4-(2-propenyl)-1H-­ carbazole-1-acetic acid methyl ester (9.71 mmol, 3.01 g) and potassium carbonate (14.57 mmol, 2.01 g) were refluxed under nitrogen for 24 hours in 78 ml of methanol and 9.7 ml of water. Most of the methanol was removed in vacuo and the residue was suspended in 15 ml of water. It was acidified to pH=1 with 1 M hydrochloric acid and extracted with 4 x 60 ml of ether. The combined ether layers were dried over magnesium sulfate and concentrated. Flash chromatography (50 mm diameter column, 25% ethyl acetate in petroleum ether eluent, 5 1/2 inches of silica gel) afforded 2.72 g (9.19 mmol, 95%) of oily product which was crystallized from 85:15 petroleum ether:benzene to afford 2.2 g of off-white powder. This powder was dried at 78°C over phosporous pentoxide for 7 hours and had m.p. 103°-105°C. Analysis: Calculated C(76.74%), H(7.79%), N(4.71%) Found C(76.84%), H(7.70%), N(4.73%) IR (KBr): 3420(NH), 3600-3000(OH), 2860-3100(-CH), 1715(C=O). Examples 5-8, 10, 11, 13-20, 22, 25, 28-32, 34, 36, 38-40 and 42 were prepared by treating cis-1-ethyl-2-oxo-4-(2-propenyl)cyclohexaneacetic acid methyl ester (Example 1, Step d) with the appropriate aryl-hydrazine in refluxing toluene for 12-100 hours to form the hydrazone of structure VII, concentration in vacuo, and dissolution in acetic acid. Treatment with boron trifluoride etherate and refluxing for 5-60 minutes afforded the compounds of structure I as their methyl esters. These were then hydrolyzed with sodium hydroxide in aqueous ethanol to afford compounds of structure I. Example 4 was prepared by treating trans-1-ethyl-2-oxo-4-(2-­ propenyl)cyclohexaneacetic acid methyl ester (prepared as in Example 1, Step d, except that aluminum trichloride was used instead of titanium tetrachloride, the reaction was carried out at 0°C to room temperature and the trans isomer was separated from the cis isomer by chromatography on silica gel) with 2-­ ethylphenylhydrazine and subsequent hydrolysis as described for Examples 5-8, 10, 11, 13-20, 22, 25, 28-32, 34, 36, 38-40, and 42. Examples 9 and 12 were prepared by treating 1- methyl-2-oxo-4-(2-­ propenyl)cyclohexaneacetic acid methyl ester (prepared as in Example 1, Step d, except that 2-methylcyclohexanone was used as the starting material in Example 1, Step b instead of 2-ethylcyclohexanone) with the appropriate hydrazine and subsequent hydrolysis as described for Examples 5-8, 10, 11, 13-20, 22, 25, 28-32, 34, 36, 38-40 and 42. Example 21 was prepared like examples 9 and 12 starting from 2-­ propylcyclohexanone instead of 2-methylcyclohexanone. Examples 23 and 35 were prepared by treating 4-(1,1-dimethyl-2-propenyl)-1-­ ethyl-2-oxocyclohexaneacetic acid methyl ester (prepared as in Example 1, Step d except that (3-methyl-2-butenyl)-tributyltin was used in place of allyltrimethylsilane) with the appropriate hydrazine and subsequent hydrolysis as described for Examples 5-8, 10, 11, 13-20, 22, 25, 28-32, 34, 36, 38-40 and 42. Examples 24 and 41 were prepared like examples 23 and 35 except that (2-­ methyl-2-propenyl)-tributyltin was used instead of (3-methyl-2-butenyl)-­ tributyltin. Examples 26 and 27 were prepared by treating 1-ethyl-2-oxo-4-­ (phenylmethyl)cyclohexaneacetic acid methyl ester (Example 2, Step a) with phenylhydrazine and subsequent hydrolysis as described for Examples 5-8, 10, 11, 13-20, 22, 25, 28-32, 34, 36, 38-40 and 42. EXAMPLE 43 cis-1,8-Diethyl-2,3,4,9-tetrahydro-9-methyl-4-(2-propenyl)-1H-­ carbazole-1-acetic acid a) Preparation of cis-1,8-Diethyl-2,3,4,9-tetrahydro-9-methyl-4-­ (2-propenyl)-1H-Carbazole-1-acetic Acid Methyl Ester Potassium hydride (5.59 mmol, 639 mg of a 35% suspension by weight in mineral oil) was washed under nitrogen with petroleum ether then stirred in 12.3 ml of THF at room temperature. cis-1,8-Diethyl-2,3,4,9-­ tetrahydro-4-(2-propenyl)-1H-carbazole-1-acetic acid, methyl ester, prepared in Example 1, Step e) (2.0 g, 5.89 mmol) was then added and the bubbling solution was stirred for 10 minutes and then treated with 30 mmol of methyl iodide (4.36 g, 1.41 ml). Thin layer chroma­ tography showed a trace of starting material remaining. KH was added until all of the starting material was consumed. The reaction was quenched with methanol then poured into water. It was extracted with ether, dried over MgSO₄ and concentrated in vacuo . Flash chromatography afforded 1.7 g (4.84 mmol, 82%) of product in the form of an oil. NMR (CDCl₃/TMS, 200MHz): 1.8 (t, 3H, J=7), 1.2 (t, 3H, J=7), 1.6-3.2 (m, 13H), 3.5 (s, 3H), 4.0 (s, 3H), 5.0-5.15 (m, 2H), 5.8-6.0 (m, 1H), 6.9-7.0 (m, 2H), 7.4(m, 1H). b) Preparation of cis-1,8-diethyl-2,3,4,9-tetrahydro-9-methyl-4-­ (2-propenyl)-1H-carbazole-1-acetic acid. A solution of the ester prepared in step a) (4.84 mmol, 1.71 g), potassium carbonate (7.26 mmol. 1 g) and 4.8 ml of water were refluxed under nitrogen in 38 ml of methanol for 24 hours. Most of the methanol was removed on a rotavap and the residue was acidified with aqueous HCl. The solution was extracted 4X with ether and the combined ether layers were dried over MgSO₄. Flash chromatography afforded 1.3 g (3.83 mmol, 80%) of yellow solid. The compound could be crystallized from 4:1 petroleum ether/benzene to afford white crystals m.p. 181-183°C. Analysis: Calculated C(77.84%) H (8.61%) N (4.13%) Found C(77.83%) H (8.41%) N (4.03%) NMR (CDCl₃/TMS, 200MHz): 1.8 (t, 3H, J=7), 1.35 (t, 3H, J=7), 1.7-3.2 (m, 13H), 4.0 (s, 3H), 5.0-5.2 (m, 2H), 5.8-6.0 9M, 1H), 7.0 (m, 2H), 7.4 (m, 1H) IR (CHCl₃): 3100-2850 (CH), 1700 (C:O). EXAMPLE 44 (1R-cis)-1,8-Diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-carbazole-1-acetic Acid Benzenemethanamine Salt (1:1) a) Preparation of (1R-cis)-1,8-Diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-­ 1H-carbazole-1-acetic Acid 2,3-Dimethoxy-strychnidin-10-one Salt (1:1) Six millimoles (1.947g) of cis-1,8-diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-­ 1H-carbazole-1-acetic acid, prepared by the process of Example 1, Step f, and 6.0mmol (2.583g) of 2,3-dimethoxy-strychnidin-10-one dihydrate (brucine dihydrate) were dissolved in 25 ml of hot ethanol. To the resultant clear solution was added 6.25ml of water and the new solution was left standing at room temperature overnight. The white crystalline salt was collected by filtration and washed with a 1:1 ethanol-water mixture (5ml). The mother liquor was used to isolate the other enantiomer in Example 45, Step a. This salt (1.94g) was taken back in hot ethanol (14 ml), and water (3.5 ml) was added dropwise while keeping the solution hot. It was left standing overnight at room temperature. The crystals thus prepared (1.73g) were collected by filtration, washed with 5 ml of a 1:1 ethanol-water mixture and dried under vacuum overnight. The yield was 80% of theory and the melting point was 128-130°C. b) (1R-cis)-1,8-Diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H- carbazole-­ 1-acetic Acid Benzenemethanamine Salt (1:1). The salt (1R-cis)-1,8-diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-­ carbazole-1-acetic acid 2,3-dimethoxy-strychnidin-10-one salt (1:1) (1.73g) was suspended in 100 ml of ether and treated with 1M hydrochloric acid with stirring. The layers were separated, and the organic layer was washed with a saturated sodium chloride (aq) solution. It was dried over sodium sulfate, filtered and evaporated to a colorless oil (765mg, 99% yield). This was dissolved in ether (5ml) and treated with a solution of benzenemethanamine (255 mg) in 2 ml of ether to give a clear solution. Upon standing at room temperature for 2 hours, a crystalline product precipitated and the solution was stored in a refrigerator overnight. The crystals were collected by filtration and washed with a small amount of ether and dried under high vacuum at room temperature to afford 715mg of the title compound (m.p. 133.5-134° C,[α] D -93°). The material was 99.9% chirally pure as determined by HPLC of the methyl ester of the free acid on a chiral chromatography column. The absolute and relative configuration were determined by x-ray crystallography. Elemental Analysis: Calculated C(77.74%) H (8.39%) N (6.48%) Found C(77.58%) H (8.16%) N (6.51%) IR (KBr) : 3340(NH), COOH (broad), 3080-2850(CH), 1640(C=O). NMR(CDCl₃,200MH z ): 0.85(t,3H,J=7.5), 1.32(t,3H,J=7.6), 1.6-2.3(m,7H), 2.6(m,2H), 2.7(m,1H), 2.80(q,2H,J=7.6), 3(m,1H), 3.86(s,2H), 4.3 (broad s), 5-5.2 (m,2H), 5.8-6(m, 1H), 6.9-7.1(m,2H), 7.2-7.4(m,6H), 9.9 (broad s,1H). EXAMPLE 45 (1S-cis)-1,8-Diethyl-2,3,4,9-tetrahydro-4- (2-propenyl)-1H-carbazole-1-acetic Acid Benzenemethanamine Salt (1:1) a) Preparation of (1S-cis)-1,8-Diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-­ carazole-1-acetic Acid 2,3-Dimethoxy-strychnidin-10-one Salt (1:1) The mother liquor from the first crystallization of Example 44, Step a, was saturated with water (5ml) and put in a refrigerator overnight. The crystals were collected by filtration and washed with a 1:1 mixture of ethanol-water (10ml) to give an enriched mixture of the brucine salt. This material was dissolved in 10ml of hot ethanol and 1ml of water was added. The solution was seeded with the product from Example 44, Step a and left at room temperature overnight. Crystals (385mg) were filtered and the mother liquor was saturated with water (30ml). The precipitate that formed (1.5g) was dissolved in 8ml of hot ethanol, treated with 3ml of water and left at room temperature overnight. The crystals were filtered, and 5ml of water were added to the filtrate. Upon crystallization overnight in the refrigerator, a white crystalline compound (1.1g) was obtained. Recrystallization twice from hot ethanol (3ml) and water (1.5ml) at room temperature afforded the brucine salt (600mg, 28% yield) 99.9% chirally pure by HPLC done on the methyl ester of the free acid. b) (1S-cis)-1,8-Diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-carbazole-1-­ acetic Acid Benzenemethanamine Salt (1:1) The brucine salt from Step a (600mg) was suspended in ether and treated with 1M hydrochloric acid. The layers were separated and the organic layer was washed with a saturated sodium chloride (aq) solution. It was dried over sodium sulfate, filtered and evaporated to give a colorless oil (265mg, 99% yield). This material was dissolved in 1.5ml of ether and treated with benzenemethanamine (88mg) in 0.5 ml of ether. Upon standing at room temperature for 2 hours and in the refrigerator overnight, a crystalline product precipitated out of solution. The crystals were collected by filtration and washed with a small amount of ether. They were dried under vacuum at room temperature to afford 248mg (70% yield, m.p. 133-134°, [α] D +91.5°, 99.9% chirally pure as determined by HPLC of the methyl ester) of the free acid of the title compound. Elemental Analysis: Calculated C(77.74%), H (8.39%), N (6.48%) Found C(77.75%), H (8.29%), N (6.49%) IR (KBr): 3340 (NH), COOH(broad), 3080-2850(CH), 1640(C=O). NMR(CDCl₃,200MH z ): 0.85(t,3H,J=7.5), 1.31(t,3H,J=7.6), 1.6-2.3 (m,7H), 2.5(m,2H), 2.65(m,1H), 2.8(q,2H,J=7.6), 3(m,1H), 3.85 (s,2H), 4.63 (broad s), 5-5.2 (m,2H), 5.8-6(m,1H), 6.9-7.1 (m,2H), 7.2-7.4 (m,6H), 10 (broad s,1H).

Claims: 1. A compound of the formula (I) wherein R¹, R², R³, R⁴, R⁵ and R⁶ are hydrogen or lower alkyl or R³ and R⁴ are joined together to form (CH₂)m or R⁵ and R⁶ are joined together to form -CH=CH-CH=CH-, (CH₂)n, -CH=CH-O- or -CH=CH-S-, R⁸ and R¹⁰ are independently hydrogen, lower alkyl or halogen, R⁹ is hydrogen or lower alkyl, m is 2 or 3, and n is 2 to 4 or a pharmaceutically acceptable salt thereof. 2. A compound according to Claim 1 characterised in that it has the formula (II) wherein R¹, R², R³, R⁴, R⁵ and R⁶ are independently hydrogen or lower alkyl containing 1 to 6 carbon atoms or R³ and R⁴ are joined together to form (CH₂)₃ or R⁵ and R⁶ are joined together to form -CH=CH-CH=CH-, (CH₂)₄, -CH=CH-O- or -CH=CH-S-, R⁸ and R¹⁰ are independently hydrogen, lower alkyl containing 1 to 6 carbon atoms or halogen, R⁹ is hydrogen or lower alkyl containing 1 to 6 carbon atoms, or a pharmaceutically acceptable salt thereof. 3. A compound according to Claim 1 characterised in that it has the formula (III) wherein R⁴, R⁵ and R⁶ are hydrogen or R⁵ and R⁶ are joined together to form -CH=CH-CH=CH-, R⁸ and R¹⁰ are independently hydrogen, methyl, ethyl or chlorine or a pharmaceutically acceptable salt thereof. 4. A compound according to Claim 1 which is 1,8-diethyl-­ 2,3,4,9-tetrahydro-4-(2-propenyl)-1H-carbazole-1-­ acetic acid or a pharmaceutically acceptable salt thereof. 5. A compound according to Claim 1 which is cis-1,8-­ diethyl-2,3,5,9-tetrahydro-4-(2-propenyl)-1H-­ carbazole-1-acetic acid or a pharmaceutically acceptable salt thereof. 6. A compound according to Claim 1 which is (1S-cis)-­ 1,8-diethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-­ carbazole-1-acetic acid, 1-ethyl-2,3,4,9-tetrahydro-­ 8-methyl-4-(2-propenyl)-1H-carbazole-1-acetic acid, cis-1-ethyl-2,3,4,9-tetrahydro-8-methyl-4-(2-propenyl)-­ 1H-carbazole-1-acetic acid, 7-chloro-1-ethyl-2,3,4,9-­ tetrahydro-8-methyl-4-(2-propenyl)-1H-carbazole-1-­ acetic acid, cis-7-chloro-1-ethyl-2,3,4,9-tetrahydro-­ 8-methyl-4-(2-propenyl)-1H-carbazole-1-acetic acid, 7,8-dichloro-1-ethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-­ 1H-carbazole-1-acetic acid, cis-7,8-dichloro-1-ethyl-­ 2,3,4,9-tetrahydro-4-(2-propenyl)-1H-carbazole-1-acetic acid, 1-ethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-­ carbazole-1-acetic acid, cis-1-ethyl-2,3,4,9-tetrahydro-­ 4-(2-propenyl)-1H-carbazole-1-acetic acid or 1,8-diethyl-­ 2,3,4,9-tetrahydro-4-(phenylmethyl)-1H-carbazole-1-­ acetic acid or a pharmaceutically acceptable salt thereof. 7. A process for the preparation of a compound claimed in Claim 1 which comprises hydrolysing an ester of formula wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁸, R⁹ and R¹⁰ are as defined in Claim 1 and R⁷ is lower alkyl and, if desired, converting a resulting acid into a pharma­ ceutically acceptable salt thereof. 8. A process as claimed in Claim 7 wherein the ester is obtained by cyclizing a hydrazone of formula wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁸, R⁹ and R¹⁰ are as defined in Claim 1 and R⁷ is lower alkyl. 9. A process for preparing a compound claimed in Claim 1 which comprises cyclising a hydrazone of formula wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁸, R⁹ and R¹⁰ are as defined in Claim 1 and if desired, converting a resulting acid into a pharmaceutically acceptable salt thereof. 10. A compound of formula wherein R¹, R², R³, R⁴, R⁵ and R⁶ are hydrogen or lower alkyl or R³ and R⁴ are joined together to form (CH₂)m or R⁵ and R⁶ are joined together to form -CH=CH-CH=CH-, (CH₂)n, -CH=CH-O- or -CH=CH-S-, R⁷ is lower alkyl, R⁸ and R¹⁰ are independently hydrogen, lower alkyl or halogen, R⁹ is hydrogen or lower alkyl, m is 2 to 3, and n is 2 to 4. 11. A pharmaceutical composition comprising a compound as claimed in any one of Claims 1 to 6 and a pharmaceutically acceptable carrier. 12. A compound as claimed in any one of Claims 1 to 6 for use as a pharmaceutical. Claims for contracting state: A 1. A process for the preparation of a compound of the formula (I) wherein R¹, R², R³, R⁴, R⁵ and R⁶ are hydrogen or lower alkyl or R³ and R⁴ are joined together to form (CH₂)m or R⁵ and R⁶ joined together to form -CH=CH-CH=CH-, (CH₂)n, -CH=CH-O- or -CH=CH-S-, R⁸ and R¹⁰ are independently hydrogen, lower alkyl or halogen, R⁹ is hydrogen or lower alkyl, m is 2 or 3, and n is 2 to 4 or a pharmaceutically acceptable salt thereof which comprises (a) hydrolysing an ester of formula wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁸, R⁹ and R¹⁰ are as defined above and R⁷ is lower alkyl, or (b) cyclising a hydrazone of formula wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁸, R⁹ and R¹⁰ are as defined above, or (c) converting an acid of formula (I) into a pharmaceutically acceptable salt thereof. 2. A process as claimed in Claim 1(a) wherein the ester is obtained by cyclizing a hydrazone of formula (VII) wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁸, R⁹ and R¹⁰ are as defined in Claim 1 and R⁷ is lower alkyl. 3. A process according to Claim 1 characterised in that the product has the formula (II) wherein R¹, R², R³, R⁴, R⁵ and R⁶ are independently hydrogen or lower alkyl containing 1 to 6 carbon atoms or R³ or R⁴ are joined together to form (CH₂)₃ or R⁵ and R⁶ are joined together to form -CH=CH-CH=CH-, (CH₂)₄ -CH=CH-O- or -CH=CH-S- R⁸ and R¹⁰ are independently hydrogen, lower alkyl containing 1 to 6 carbon atoms or halogen, R⁹ is hydrogen or lower alkyl containing 1 to 6 carbon atoms, or a pharmaceutically acceptable salt thereof. 4. A process according to Claim 1 characterised in that the product has the formula (III) wherein R⁴, R⁵and R⁶ are hydrogen or R⁵ and R⁶ are joined together to form -CH=CH-CH=CH-, R⁸ and R¹⁰ are independently hydrogen, methyl, ethyl or chlorine or a pharmaceutically acceptable salt thereof. 5. A process according to Claim 1 characterised in that the product is 1,8-diethyl-2,3,4,9-tetrahydro-4-­ (2-propenyl)-1H-carbazole-1-acetic acid or a pharma­ ceutically acceptable salt thereof. 6. A process according to Claim 1 characterised in that the product is cis-1,8-diethyl-2,3,4,9-tetrahydro-4-­ (2-propenyl)-1H-carbazole-1-acetic acid or a pharma­ ceutically acceptable salt thereof. 7. A process according to Claim 1 characterised in that the product is (1S-cis)-1,8-diethyl-2,3,4,9-tetrahydro-­ 4-(2-propenyl)-1H-carbazole-1-acetic acid, 1-ethyl-­ 2,3,4,9-tetrahydro-8-methyl-4-(2-propenyl)-1H-­ carbazole-1-acetic acid, cis-1-ethyl-2,3,4,9-­ tetrahydro-8-methyl-4-(2-propenyl)-1H-carbazole-1-­ acetic acid, 7-chloro-1-ethyl-2,3,4,9-tetrahydro-8-­ methyl-4-(2-propenyl)-1H-carbazole-1-acetic acid, cis-7-chloro-1-ethyl-2,3,4,9-tetrahydro-8-methyl-4-­ (2-propenyl)-1H-carbazole-1-acetic acid, 7,8-dichloro-­ 1-ethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-carbazole-­ 1-acetic acid, cis-7,8-dichloro-1-ethyl-2,3,4,9-­ tetrahydro-4-(2-propenyl)-1H-carbazole-1-acetic acid, 1-ethyl-2,3,4,9-tetrahydro-4-(2-propenyl)-1H-carbazole-­ 1-acetic acid, cis-1-ethyl-2,3,4,9-tetrahydro-4-­ (2-propenyl)-1H-carbazole-1-acetic acid or 1,8-diethyl-­ 2,3,4,9-tetrahydro-4-(phenylmethyl)-1H-carbazole-1-­ acetic acid or a pharmaceutically acceptable salt thereof. 8. A process for preparing a compound of formula wherein R¹, R², R³, R⁴, R⁵, R⁶ are hydrogen or lower alkyl or R³ and R⁴ are joined together to form (CH₂)m or R⁵ and R⁶ are joined together to form -CH=CH-CH=CH-, (CH₂)n, -CH=CH-O- or -CH=CH-S-, R⁷ is lower alkyl, R⁸ and R¹⁰ are independently hydrogen, lower alkyl or halogen, R⁹ is hydrogen or lower alkyl, m is 2 or 3, and n is 2 to 4, which comprises treating a compound of formula (VII) wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as defined above with a cyclizing agent. 9. A process for preparing a pharmaceutical composition characterised in that a compound of formula (I) as defined in Claim 1 or a pharmaceutically acceptable salt thereof is brought into association with a pharmaceutically acceptable carrier. 10. A process for preparing a pharmaceutical composition characterised in that a compound of formula (I) or a pharmaceutically acceptable salt thereof is prepared by a process claimed in any one of Claims 1 to 7 and the resulting compound is brought into association with a pharmaceutically acceptable carrier.

Inventors: DEMERSON, CHRISTOPHER ALEXANDER, HUMBER, LESLIE GEORGE, MOBILIO, DOMINICK
Applicants: AMERICAN HOME PRODUCTS CORPORATION
Application year: 1986
Main classification: C07D209
IPC codes: A61P29, C07D209, A61K31