NO790083L - METHODS OF PREPARING SUBSTITUTED 1,4-CYCLOHEXADIENE-CARBOXYLIC ACID DERIVATIVES - Google Patents

Description

The present invention relates to new substituted 1,4-cyclohexadienecarboxylic acid derivatives which exhibit useful pharmacological properties.

Several previous studies have shown that γ-aminobutyric acid is a main inhibitory transmission in the central nervous system as described by e.g. S. Kranjevic, Physiological Reviews 54, 418 - 540

(1974), and that disturbance in the interaction of stimulation and inhibition can lead to morbid conditions such as Huntington's dementia (The Lancet, 9 November 1974, pp. 1122 - 1132), Parkinsonism, schizophrenia, epilepsy, depression, hyperkinesis and manic depression disorders, E. Roberts, Biochem, Pharmacol. 23, 2637-2649 (1974). Certain compounds are known to increase brain concentrations of γ-aminobutyric acid, e.g. n-dipropyl acetate (Simler et al., Biochem. Pharm., 22 1701 (1973) by competitive inhibition of γ-aminobutyric acid transaminase leading to a reversible effect lasting only 2 hours. Also 4-aminotetrolic acid (P. M. Beart et al., J . Neurochem. 19 1849 (1972)) known to be a competitive reversible inhibitor of γ-aminobutyric acid transaminase.

US Patents 3,959,356 and 3,960,927 respectively cover acetylenic and olefinic derivatives of amino acids which are irreversible inhibitors of γ-aminobutyric acid transaminase.

The natural product gabaculin or 5-amino-1,3-cyclohexadiene-1-carboxylic acid is known to be a selective irreversible inhibitor of γ-aminobutyric acid transaminase in vitro and in vivo (Kobayashi et al., Tetrahedron letters 1976, 537;

R. Rando and F.W. Bangerter, Biochem. Biophys. Res. Comm. 76, 1276 (1977), and J. Am. Chem. Soc. 98, 6762 (1976), Kobayashi et al., FEBS, Lett. 76, 207 (1977), in that gabaculin acts as a substrate for the transaminase. Gabaculine thus prevents the consumption of 4-aminobutyric acid, which consumption is associated with central nervous system diseases such as Parkinson's disease and epilepsy.

It has now been found that compounds according to the invention t have irreversible inhibitors of γ-aminobutyric acid transaminase and which exhibit a better effect than gabaculin and certain other known irreversible inhibitors of γ-aminobutyric acid transaminase, which makes the compounds particularly useful in the treatment of the above-mentioned disease states.

The compounds according to the invention are represented by the following general formula in:

in which is hydrogen, alkylcarbonyl in which the alkyl moiety has from 1 to 4 carbon atoms and is straight-chain or branched, alkoxycarbonyl in which the alkoxy moiety has from 1 to 4 carbon atoms and is straight-chain or branched, or the radical in which R^ is hydrogen, a straight-chain or branched alkyl group with from 1 to 4 carbon atoms, benzyl or p-hydroxybenzyl, and R2 is hydroxy, a straight-chain or branched alkoxy group of from 1 to 8 carbon atoms, in which each of R^ and R,- is hydrogen or a straight-chain or branched alkyl group of from 1 to 4 carbon atoms or the radical

wherein Rg is hydrogen, a straight or branched alkyl group having from 1 to 4 carbon atoms, benzyl or p-hydroxybenzyl. The pharmaceutically acceptable salts of the compounds of general formula

I is also included within the scope of the invention.

Illustrative examples of straight-chain lower alkyl groups with from 1 to 4 carbon atoms are methyl, ethyl, n-propyl and n-butyl, and examples of branched lower alkyl groups with from 1 to 4 carbon atoms are isopropyl, isobutyl, and tert-butyl.

Illustrative examples of straight-chain lower alkoxy groups with from 1 to 4 carbon atoms are methoxy, ethoxy, n-propoxy and n-butoxy, and examples of branched lower alkoxy groups with from 1 to 4 carbon atoms are isopropoxy, isobutoxy and tert-butoxy.

Illustrative examples of straight-chain or branched alkoxy groups with from 1 to 8 carbon atoms are methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, neopentoxy, pentoxy, octyloxy, heptyloxy and hexyloxy.

Illustrative examples of pharmaceutically acceptable salts of the compounds of the invention include non-toxic acid addition salts formed with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid and phosphoric acid, and organic acids such as trifluoroacetic acid, methanesulfonic acid, salicylic acid, maleic acid, malonic acid, tartaric acid, citric acid and ascorbic acid, and non-toxic salts formed with inorganic and organic bases, such as salts of alkali metals, e.g. sodium, potassium and lithium, alkaline earth metals, e.g. calcium and magnesium, light metals from group HIA, e.g. aluminium, organic amines such as primary, secondary or tertiary amines, e.g. cyclohexylamine, ethylamine, pyridine, methylaminoethanol, ethanolamine and piperidine. The salts of the compounds according to the invention are prepared in a known manner.

Illustrative examples of compounds according to the invention are the following:

3-amino-1,4-cyclohexadiene-carboxylic acid,

methyl or ethyl 3-amino-1,4-cyclohexadienecarboxylate, N-methyl-3-amino-1,4-cyclohexadienecarboxamide,

N-ethyl-3-amino-1,4-cyclohexadienecarboxamide,

N-propyl-3-amino-1,4-cyclohexadienecarboxamide,

N,N-di-n-butyl-3-amino-1,4-cyclohexadienecarboxamide, methyl 3-(tert-butoxycarbonylamino)-1,4-cyclohexadienecarboxylate, 3-amino-1,4-cyclohexadienecarboxamide,

N-(3-amino-1,4-cyclohexadienyl)carbonylalanine, 3-acetamido-1,4-cyclohexadiene-carboxylic acid and

3-alanylamino-1,4-cyclohexadiene carboxylic acid.

Preferred compounds according to the invention are those in which R is hydrogen or alkylcarbonyl. Another preferred embodiment of the present invention are compounds in which R£ is hydroxy or a straight-chain or branched alkoxy group. The most preferred embodiment of the invention are compounds in which R 1 is hydrogen and R 2 is hydroxy, and salts thereof.

The compounds according to the invention have numerous pharmacological applications. The compounds of the invention are useful as sedatives. The compounds of general formula I and pharmaceutically acceptable salts thereof are useful as inhibitors of γ-aminobutyric acid transaminase leading to an increase in brain concentration of γ-aminobutyric acid which makes such compounds useful in the treatment of disorders of the central nervous system functions consisting of involuntary movements such as Huntington's Christmas dance, Parkinsonism, extrapyramidal effects of drugs, e.g. neuroleptics, seizure disorders associated with epilepsy, alcohol withdrawal and barbiturate withdrawal, psychosis associated with schizophrenia, depression and manic depression and hyperkinesia. The compounds according to the invention are also useful as hypothermic agents, muscle relaxants, cholinergic agents, antibacterial agents, anticonvulsant agents, analgesics, anorexic agents, anti-obesity agents, tranquilizers, sedatives and central nervous system stimulants.

The sedative properties of the compounds according to the invention can be determined by measuring spontaneous motor activity in rodents by the procedures described by P. Dews. Brit.

J. Pharmacol. 8, 46 (1953) by administering the compound either intravenously, intraperitoneally or orally to mice or rats.

The ability of the compounds of general formula I to inhibit γ-aminobutyric acid transaminase can be determined by in vitro or in vivo measurements of γ-aminobutyric acid transaminase activity. For example, γ-aminobutyric acid concentrations in the brain of mice and rats can be determined after treatment with the compound. The γ-amino-butyric acid transaminase inhibitory effect of the compounds of formula I can also be shown by the protective effect of treatment of audiogenic seizures in mice of the DBA strain measured by the general method described by Simler et al., Biochem. Pharmacol. 22, 1701

(1973) which hppig is used as a proof of antiepileptic activity.

The ability of compounds of general formula I to alleviate reserpine ptosis can be demonstrated by the classic test described by B. Rubin et al., J. Pharmacol. 120, 125 (1957) which is frequently used to determine antidepressant activity.

As indicated above, it has been found that the compounds according to the invention provide certain advantages compared to gabaculin, which is a known inhibitor of γ-aminobutyric acid transaminase, in that the compounds according to the invention are more effective inhibitors of the enzyme. Compounds according to the invention also contain conjugated double bonds and are thus expected to complex less easily with macromolecules such as DNA or RNA. The compounds according to the invention are particularly effective in reducing γ-aminobutyric acid transaminase activity and increasing γ-aminobutyric acid concentrations in the brain.

The compounds according to the invention can be administered in different ways to the patient being treated to achieve the desired effect. The compounds can be administered alone or in the form of a pharmaceutical preparation orally, parenterally, e.g. intravenously, intraperitoneally, subcutaneously or topically. The amount of compound administered will vary over a wide range and may be any effective amount. Depending on the patient being treated, the condition to be treated and the method of administration, the effective amount of the administered compound will vary from 0.1 mg/kg to 150 mg/kg body weight per unit dose, and will preferably be 10 mg/kg to 100 mg/kg body weight per unit dose. A typical unit dose can e.g. be a tablet containing from 10 to 200 mg of a compound of formula I which can be administered to the patient from 1 to 4 times a day to achieve the desired effect.

As indicated here, the term patient means warm-blooded animals such as mammals, e.g. cats, females, rats, mice, March wine, horses, cattle and sheep.

The fixed unit dosage forms can be of the usual type. Thus, the solid form can be a capsule which can be the usual gelatin type containing a new compound according to the invention and a carrier, e.g. lubricants and inert fillers such as lactose, sucrose and corn starch. In another embodiment, the new compounds are tableted with common tablet bases such as lactose, sucrose or corn starch in combination with binders such as acacia, corn starch or gelatin, disintegrants such as corn starch, potato starch or alginic acid, and a lubricant such as stearic acid or magnesium stearate .

For parenteral administration, the compounds may be administered as injectable doses of a solution or suspension of the compound in a physiologically acceptable diluent with a pharmaceutical carrier which may be a sterile liquid such as water and oil with or without the addition of a lubricant and other pharmaceutically acceptable excipients. Illustrative examples of oils that can be used in these preparations are petroleum oils, animal, vegetable or synthetic oils, e.g. peanut oil, soybean oil and mineral oil. In general, water, physiological saline, aqueous dextrose and related sugar solutions, ethanol and glycols such as propylene glycol or polyethylene glycol are preferred as liquid carriers for injectable solutions.

The compounds can then be administered in the form of a depot injection or implanted preparation that can be formulated on

such a way that a delayed release of the active ingredient is enabled. The active ingredient can be pressed into pellets or small cylinders and implanted subcutaneously or intramuscularly as depot injections or implants. Implants can use inert materials such as biodegradable polymers or synthetic silicones.

Illustrative examples of pharmaceutical preparations containing the compounds according to the invention are given below.

Part of the wheat starch is used to produce a granulated starch paste which, together with the remaining wheat starch and the lactose, is granulated, sieved and mixed with the active ingredient (a) and the magnesium stearate. The mixture is pressed into tablets each weighing 150 mg.

An illustrative composition for parenteral injection is as follows, in which the amounts are on a weight to volume basis:

The composition is prepared by dissolving the active ingredient (a) and sufficient sodium chloride in water for injection to make the solution isotonic. The composition can be dispensed in a single ampoule containing 50 mg of active ingredient for multiple dosing, or in 20 ampoules for single dosing.

An illustrative composition for hard gelatin capsules is as follows:

The composition is prepared by passing the dry powders of (a) and (b) through a fine sieve and mixing them well. The powder is then filled into hard gelatin capsules No. 0 to a net filling of 135 mg per capsule.

The preparation of the compounds of general formula I in which is hydrogen and R2 is hydroxy is illustrated by the following reaction core:

In the above-mentioned reaction scheme, R denotes a straight-chain or branched alkoxy group with from 1 to 6 carbon atoms, benzyloxy, p-methoxybenzyloxy or 2,4-dimethoxybenzyloxy, Ar is phenyl or p-methoxyphenyl, HA denotes an inorganic acid such as hydrochloric acid, hydrobromic acid or trifluoroacetic acid, and t-Bu is tertiary butyl. Illustrative examples of straight-chain or branched alkoxy groups with from 1 to 6 carbon atoms that R can represent are methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, n-pentoxy and n-hexyloxy. The 4-phenylsulfinyl-2-cyclohexenecarboxylic acid ester, compound (1) is reacted with silver cyanate in the presence of solid iodine in a solvent such as methylene chloride, chloroform, carbon tetrachloride, tetrahydrofuran or diethyl ether at -10 to 25°C for 3 to 24 hours to form of 2-iodo-3-isocyano-4-phenylsulfinyl carboxylic acid esters, compound (2) to which benzyl alcohol or p-methoxybenzyl alcohol is added with stirring for 6 - 18 hours, optionally in the presence of a catalyst, such as diisobutyltin dilaurate or benzyloxylithium or p-methoxybenzyloxylithium to form benzyl or p-methoxybenzylcarmarate, compound (3). The carbamate is treated with 1 equivalent

of a hindered base such as triethylamine, diazabicyclooctane, diazabicyclononene, or diazabicycloundecene, in a solvent such as acetone, ether, tetrahydrofuran, methylene chloride, chloroform or dioxane at approx. 25° C for 1 to 4 hours during formation of the dehydrodeiodinated derivative, compound (4) which is heated to 6 0 - 14 0° C for approx. 1/2 hour to 24 hours in a solvent such as chlorinated hydrocarbons, e.g. carbon tetrachloride or atomic hydrocarbons such as xylene or toluene to form the 1,4-diene derivative, compound (5). The diene derivative is treated with excess acid, e.g. hydrochloric acid, hydrobromic acid or trifluoroacetic acid, the latter being preferred, in excess of anispl or excess of 1,3-dimethoxybenzene to form the acid addition salt (6). When R in the acid addition salt is different from tert-butoxy, benzyloxy, p-methoxybenzyloxy or 2,4-dimethoxybenzyloxy, the acid addition salt or 3-amino-1,5-cyclohexadiene-carboxylic acid ester salt compound (6) is reacted with 2-tert-butoxycarbonyloxyimino-2-phenylacetonitrile or tert-butyl azidoformate in the presence of a base, such as an alkylamine, e.g. triethylamine, sodium hydroxide or potassium hydroxide in a solvent such as ethers, e.g. diethyl ether, tetrahydrofuran or dioxane, dimethylformamide, chlorinated hydrocarbons such as methylene chloride or chloroform at approx. 25° C for 1 - 24 hours followed by alkaline hydrolysis and then acid hydrolysis, and when the free base is desired, the base is treated according to methods known in the art. Alkali hydrolysis can be carried out e.g. by treatment with sodium hydroxide or potassium hydroxide for 1 - 3 hours at approx. 25° C, or with trimethylsilyl iodide in carbon tetrachloride or chloroform^ at approx. 25 - 50° C for 4 - 40 hours during formation of the carbamatic acid, compound (8). Acid hydrolysis of the carbamic acid can be achieved e.g. by treatment with hydrochloric acid, hydrobromic acid or trifluoroacetic acid in a lower alcohol for 1 - 20 hours at temperatures up to the reflux temperature. When R in the ester carbamate (5) is tertiary butoxy-benzyloxy, p-methoxybenzyloxy or 2,4-dimethoxy-. benzyloxy, the derivative can be treated with trifluoroacetic acid in the presence of anisole and then transferred directly to an ion exchange resin to form the 3-amino-1,4-cyclohexadienecarboxylic acid derivative of formula I.

To obtain 4-phenylsulfinyl-2-cyclohexenecarboxylic acid esters, compound (1), the corresponding esters of 2-trimethylsilyloxy-3-cyclohexenecarboxylic acid are prepared by reacting trimethylsilyloxybutadiene with a suitable acrylate by the general procedure described by P. Cazean and E. Frainnet, Bull, Soc. Chim. Fr. 1972, p. 1658, after which the ether splits, e.g. by treatment with 2M hydrochloric acid in methanol il - 10 minutes at approx. 25° C, or by treatment with a dilute base such as 0.5 M sodium hydroxide in aqueous methanol (1:1) for 5 - 10 minutes at approx. 25° C. The hydroxyester thus obtained is then treated with benzenesulfinyl chloride in the presence of a base such as triethylamine in methylene chloride, forming the 4-phenylsulfinyl derivative. Other hindered amine bases such as diazabicyclooctane, diazabicyclononene or diazabicycloundecene may be used, and other suitable solvents include chloroform, ether, tetrahydrofuran and benzene. The reaction time varies from 5 minutes to 1 hour at a temperature of 0 - 25° C. Alternatively, the hydroxy ester can be converted to the corresponding sodium alkoxide by treatment with sodium hydride in ether or tetrahydrofuran followed by reaction with benzene sulphenyl chloride as described here.

The compounds of general formula I in which R2 is a straight-chain or branched alkoxy group with from 1 to 8 carbon atoms are prepared from the corresponding derivative in which R2 is hydroxy by reaction with an alcohol of the formula R^OH in which R7 is a straight-chain or branched alkyl group with from 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, neopentyl, or n-hexyl, saturated with HCl gas at approx. 25° C for 12 - 36 hours.

The compounds of general formula I in which R2 is NR^Rj-in which each of R^ and R1- is hydrogen or a lower alkyl group with from 1 to 4 carbon atoms, are prepared by treating a functional derivative of the corresponding compound in which R2 is hydroxy, e.g. e.g. an acid halide such as the acid chloride or an acid anhydride, and R-^ has the meaning given in formula I, with an excess of an amine of the formula HNR^R^ in which R^ and R,- have the meanings given above, provided that any free amino group is suitably protected. The reaction is carried out in a solvent such as methylene chloride, chloroform, dimethylformamide or ethers, such as tetrahydrofuran and dioxane or benzene at approx.

25° C for 1 - 4 hours. Suitable amines are ammonia, or a compound which is a potential source of ammonia such as hexamethylenetetramine, primary amines, e.g. methylamine, ethylamine or m-propylamine, and secondary amines, e.g. dimethylamine, diethylamine or di-n-butylamine. After the reaction, the amine protecting groups are removed by treatment with acid, e.g. trifluoroacetic acid or hydrogen bromide in dioxane.

The compounds of general formula I in which R 2 is

in which Rg is hydrogen, a straight-chain or branched lower alkyl group with from 1 to 4 carbon atoms, benzyl or p-hydroxybenzyl, produced by reacting an acid anhydride of the corresponding derivative in which R2 is hydroxy, and R-^ has the meaning given in formula I, provided that any free amino group is protected with a suitable blocking group such as benzyloxycarbonyl or tert-butoxycarbonyl, with a compound of the formula wherein Rg is as defined above and Rg is a lower alkyl group such as methyl or ethyl in an ether solvent such as tetrahydrofuran or dioxane, in the presence of a base such as triethylamine at 0-50°C for 1-24 hours followed by acid hydrolysis, e.g. with trifluoroacetic acid or hydrogen bromide in dioxane, and base hydrolysis using e.g. sodium hydroxide or sodium borate at a temperature of 0 - 25° C for 1/2 hour to 6 hours. The compounds of general formula I in which is alkylcarbonyl in which the alkyl part has from 1 to 4 carbon atoms and is straight-chain or branched and where R 2 is hydroxy or an alkoxy group with from 1 to 8 carbon atoms, are prepared by treating the corresponding derivative in which R-^ is hydrogen, with an acid halide of the formula wherein halo is a halogen atom such as chlorine or bromine, and Rg is a straight-chain or branched alkyl group having from 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl and tert-butyl , or a suitable acid anhydride, in water in the presence of a base such as sodium hydroxide or sodium borate, or in dichloromethane in the presence of an amine base such as triethylamine at a temperature of 0 to 25° C. for 1/2 hour to 24 hours. The compounds of general formula I in which R-^ is alkoxycarbonyl in which the alkoxy part is straight-chain or branched and has from 1 to 4 carbon atoms, is prepared by treating the corresponding derivative in which R- is a lower alkoxy group such as methoxy e ller ethoxy, and where R^ is hydrogen, with an alkylhaloformate of the formula wherein R^q is a straight-chain or branched alkyl group having from 1 to 4 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl or tert -butyl, and halo is halogen such as chlorine or bromine, in water in the presence of a base such as sodium hydroxide or sodium borate, or in dichloromethane in the presence of an amine base such as triethylamine, at a temperature of 0 - 25° C in 1/ 2 hours to 6 hours, followed by base hydrolysis using e.g. sodium hydroxide or sodium borate at a temperature of 0 to 25°C for 1/2 hour to 6 hours. The compounds of general formula I in which R 2 is hydrogen, a straight-chain or branched alkyl group of from 1 to 4 carbon atoms, benzyl or p-hydroxybenzyl, are prepared by treating the corresponding derivative in which R 2 is a lower alkoxy group such as methoxy or ethoxy, and R^ is hydrogen, with an acid of the formula

or an anhydride

thereof, in which the amino group is protected with a suitable blocking group such as benzyloxycarbonyl or tert-butoxycarbonyl, and where R^ has the meaning given above, in an ether such as tetrahydrofuran or dioxane, or a chlorinated hydrocarbon such as methylene chloride or chloroform, and in presence of a dehydrating agent such as dicyclohexylcarbodiimide when the free acid is used, at a temperature of 0-35°C for 1-12 hours, followed by base hydrolysis, e.g. using sodium hydroxide or sodium borate, and acid hydrolysis using e.g. trifluoroacetic acid or HBr-/dioxane at a temperature of 0 - 25°C for 1/2 to 6 hours.

The following examples illustrate the invention.

Example 1

3-amino-1,4-cyclohexadieri-carboxylic acid

A solution of 2 g (10 mmol) methyl 2-trimethylsilyloxy-2-cyclohexene carboxylate in 10 ml methanol was treated with 1N hydrochloric acid for 1 hour at 25° C. and then concentrated under reduced pressure and extracted with ether. The organic solution was dried over magnesium sulfate and concentrated. The resulting residue was dissolved in 20 ml of dichloromethane and treated with 1.0 g (10 mmol) of triethylamine followed by 1.44 g (10 mmol) of phenylsulphenyl chloride. After 1 hour at 25° C, the solution was washed with water, dried and concentrated to form methyl-4-phenyl-sulfinyl-2-cyclohexenecarboxylate.

To 2.6 g (10 mmol) of methyl-4-phenylsulfinyl-2-cyclohexenecarboxylate in 20 ml of dichloromethane at 0° C was added. 2 g (13 mmol) of silver cyanate followed by 2.5 g (10 mmol) of iodine in small portions. The mixture was stirred at 0°C for 1 hour at 25°C for 4 hours and then filtered through celite. The solution was concentrated after which 1.4 g (10 mmol) of p-methoxybenzyl alcohol was added. The mixture was stirred for approx. 16 hours at 25°C after which 50 ml of acetone was added followed by 1.1 g (10 mmol) of diazabicyclooctane. After 2 hours at 25° C., the solvent was evaporated, and the residue was taken up in ether and water. The organic phase was dried and evaporated to give a residue which was taken up in toluene and heated to reflux for 45 minutes, after which the solvent was removed under reduced pressure and the residue chromatographed on silica gel to give methyl-3-(p-methoxybenzyloxycarbonylamino) -1,4-cyclohexadienecarboxylate.

A solution of 640 mg (2 mmol) of methyl 3-(p-methoxybenzyloxycarbonylamino)-1,4-cyclohexadienecarboxylate in 5 mL of anisole was treated with 5 mL of trifluoroacetic acid for 1 hour at 0° C., after which the solvent was removed in vacuum and the resulting oil residue was treated with ether to give a precipitate which was collected to give methyl 3-amino-1,4-cyclohexadienecarboxylate-trifluoroacetate. A solution of 500 mg (2.3 mmol) of the amine trifluoroacetate in 2 ml of dimethylformamide was treated with 300 mg (2.3 mmol) of tert-butyl azidoformate for approx. 16 hours at 25°C, after which the solvent was removed under reduced pressure. The residue was taken up in ether and washed with water. The ether solution was dried and evaporated to give methyl 3-tert-butoxycarbonylamino-1,4-cyclohexadienecarboxylate, of which 400 mg was taken up in 2 ml of methanol containing 200 mg of sodium hydroxide and 1.5 ml of water and stirred at 25°C for 2 hours and then acidified with IN HC1. The resulting precipitate was collected (200 mg) and dissolved in 4 ml of methanol. The solution was treated with 2 ml of 2N HCl at 25°C for 24 hours and was then diluted with acetone to form 3-amino-1,4-cyclohexadiene carboxylic acid.

Example 2

Ethyl-3-amino-1,4-cyclohexadienecarboxylate hydrochloride

200 mg of 3-amino-1,4-cyclohexadiene-carboxylic acid hydrochloride was dissolved in ethanol containing anhydrous HCl, and the resulting solution was stirred overnight at 0° C. Evaporation of the solvent gave ethyl-3-amino-1,4 -cyclohexadiene carboxylate hydrochloride.

Example 3

N-propyl-3-amino-1,4-cyclohexadienecarboxamide hydrochloride

A solution of 240 mg (1 mmol) of 3-tert-butoxy-carbonyl-amino-1,4-cyclohexadiene-carboxylic acid in 5 ml of dichloromethane was treated with 202 mg (2 mmol) of triethylamine and 94 mg (1 mmol) of methyl chloroformate. After 30 minutes at 25° C., the solution was treated with 60 mg (1 mmol) of n-propylamine for 1 hour at 25° C., after which the solution was diluted with dichloromethane, washed with water, dried and evaporated. The residue was stirred for 18 hours in 7 ml of methanol and 3.5 ml of 5% aqueous HCl. Evaporation gave N-propyl-3-amino-1,4-cyclohexadienecarboxamide hydrochloride.

Example 4

N-(3-amino-1,4-cyclohexadienyl)carbonylalanine hydrochloride

A solution of 240 mg (1 mmol) of 3-tert-butoxycarbonyl-amino-1,4-cyclohexadiene-carboxylic acid and 5 ml of dichloromethane was treated with 202 mg (2 mmol) of triethylamine and 94 mg (1 mmol) of methyl chloroformate. After 30 minutes at 25° C., the solution was treated with 103 mg (1 mmol) alanine methyl ester and kept at 25° C. for 1 hour, after which the solution was washed with water, dried and concentrated. The residue was treated with 3 ml of methanol and 120 mg of sodium hydroxide in 2 ml of water for 3 hours at 25° C. and then acidified and extracted with dichloromethane. The organic phase was dried and concentrated. The residue was treated with 7 ml of methanol containing 5% HCl for 18 hours at 25° C. Evaporation gave N-(3-amino-1,4-cyclohexadienyl)carbonylalanine hydrochloride.

Example 5

3-acetamido-1,4-cyclohexadiene carboxylic acid

A solution of 190 mg (1 mmol) methyl-3-amino-1,4-cyclohexadienecarboxylate hydrochloride in 5 ml dichloromethane was treated with 78 mg (1 mmol) acetyl chloride and 202 mg (2 mmol) triethylamine for 1 hour at 25° C, after which the solution was washed with water, dried and concentrated. The residue was treated at 25° C. with 3 ml of methanol and 100 ml of sodium hydroxide in 200 ml of water for 3 hours, and then transferred to solid material and extracted with dichloromethane. The organic phase was dried and evaporated to give 3-acetamido-1,4-cyclohexadiene-carboxylic acid.

Example 6

3-alanylamino-1,4-cyclohexadiene-carboxylic acid hydrochloride

A solution of 188 mg (1 mmol) of tert-butoxycarbonylalanine in 5 ml of dichloromethane was treated with 101 ml (1 mmol) of triethylamine and 94 mg (1 mmol) of methyl chloroformate and then added to a solution of 190 mg (1 mmol) of methyl-3 -amino-1,4-cyclohexadienecarboxylate hydrochloride and 101 mg (1 mmol) of triethylamine in 5 ml of dichloromethane. After 1 hour at 25° C., the solution was washed with water, dried and evaporated. The residue was treated for 3 hours at 25°C with 3 ml of methanol, 100 mg of sodium hydroxide and 2 ml of water, and then acidified and extracted with dichloromethane. The organic phase was dried and concentrated. The residue was treated with 7 ml of methanol containing 3.5 ml of 5% HCl for 18 hours at 25° C. and then concentrated to form 3-alanylamino-1,4-cyclohexadiene-carboxylic acid hydrochloride.

Example 7-

N-propyl-3-acetamido-1,4-cyclohexadienecarboxamide

A solution of 180 mg (1 mmol) of 3-acetamido-1,4-cyclohexadienecarboxylic acid in 5 ml of dichloromethane was treated with 202 mg (2 mmol) of triethylamine and 94 mg (1 mmol) of methyl chloroformate. After 30 minutes at 25° C, the solution was treated with 60 mg (1 mmol) of n-propylamine for 1 hour at 25° C, after which the solution was diluted with dichloromethane, washed with water, dried and evaporated to form N-propyl- 3-acetamido-1,4-cyclohexadiene-carboxamide.

Example 8

N- propyl- 3-( 2- aminopropionamido)- 1, 4- cyclohexadiene- carboxamide-trifluoroacetate

A solution of 310 mg (1 mmol) of 3-(2-tert-butoxy-carbonyl-aminopropionylamido)-1,4-cyclohexadiene-carboxylic acid in 5 ml of dichloromethane was treated with 202 mg (2 mmol) of triethylamine and 94 mg (1 mmol) methyl chloroformate. After 30 minutes at 25° C., the solution was treated with 60 mg (1 mmol) of n-propylamine for 1 hour at 25° C., after which the solution was diluted with dichloromethane and washed with water. The organic phase was dried and concentrated to give a residue which was treated with 2 ml of trifluoroacetic acid for 1 hour at 25°C and then diluted with anhydrous ether. The precipitated trifluoroacetate salt was filtered off to form N-propyl-3-(2-aminopropionamide)-1,4-cyclohexadienecarboxamide trifluoroacetate.

Example 9

N-(2- propionic acid)- 3- acetamido- 1, 4- cyclohexadiene- carboxamide

A solution of 180 mg (1 mmol) of 3-acetamido-1,4-cyclohexadienecarboxylic acid in 5 ml of dichloromethane was treated with 202 mg (2 mmol) of triethylamine and 94 mg (1 mmol) of methyl chloroformate. After 35 minutes at 25° C., the solution was treated with 103 mg

(1 mmol) alanine methyl ester and kept at 25° C. for 1 hour, after which the solution was washed with water, dried and concentrated. The resulting residue was treated with 3 ml of methanol and 120 mg of sodium hydroxide in 2 ml of water for 3 hours at 25°C, then acidified and extracted with dichloromethane. The organic phase was dried and concentrated to give N-(2-propionic acid)-3-acetamido-1,4-cyclohexadienecarboxamide.

Example 10

N-(2- propionic acid)- 3-(2- aminopropionamido)- 1, 4- cyclohexadienecarboxamide- trifluoroacetate

A solution of 310 mg (1 mmol) of 3-(2-tert-butoxycarbonyl-aminopropionylamido)-1,4-cyclohexadiene-carboxylic acid in 5 ml of dichloromethane was treated with 202 mg (2 mmol) of triethylamine and 94 mg (1 mmol) of methyl chloroformate. After 30 minutes at 25° C., the solution was treated with 103 mg (1 mmol) alanine methyl ester and kept at 25° C. for 1 hour, after which the solution was washed with water, dried and concentrated. The resulting residue was treated with 3 ml of methanol and 120 mg of sodium hydroxide in 2 ml of water for 3 hours at 25°C and then acidified and extracted with dichloromethane. The organic phase was dried and concentrated to give a residue which was treated with 2 ml of trifluoroacetic acid for 1 hour at 25°C and then diluted with anhydrous ether. The precipitated trifluoroacetate salt was filtered off to give N-(2-propionic acid)-3-(2-aminopropionamido)-1,4-cyclohexadienecarboxamide trifluoroacetate.

The individual optical isomers of general formula I are included within the scope of the invention. These can be prepared from the racemate using (+) or (-) binaphthylphosphoric acid as described by R. Viterbo et al., Tetrahedron Letters 48, 4617 - 4620 (1971) and in US Patent 3,848,030. Other solvents such as (+) camphor-10-sulfonic acid can also be used.

Claims (7)

1. Connection of the formula in which R-^ is hydrogen, alkylcarbonyl in which the alkyl moiety has from 1 to 4 carbon atoms and is straight-chain or branched, alkoxycarbonyl in which the alkoxy moiety has from 1 to 4 carbon atoms and is straight-chain or branched, the group in which R^ is hydrogen, a straight-chain or branched alkyl group of from 1 to 4 carbon atoms, benzyl or p-hydroxybenzyl, and where R_ is hydroxy, a straight-chain or branched alkoxy group of from 1 to 8 carbon atoms, -NR^R^ in which each of R^ and R^ are hydrogen or a straight-chain or branched alkyl group having from 1 to 4 carbon atoms, or the group wherein Rg is hydrogen, a straight-chain or branched alkyl group having from 1 to 4 carbon atoms, benzyl or p-hydroxybenzyl, and pharmaceutically acceptable salts and individual optical isomers thereof. 2. Compound according to claim 1, characterized in that R 1 is hydrogen or alkylcarbonyl. 3. Compound according to claim 1, characterized in that R 2 is hydroxy or a straight-chain or branched alkoxy group. 4. Compound according to claim 1, characterized in that this is 3-amino-1,4-cyclohexadienecarboxylic acid and pharmaceutically acceptable salts thereof. 5. Compound according to claim 4, characterized in that this is 3-amino-1,4-cyclohexadiene-carboxylic acid-trifluoroacetate. 6. Process for producing a compound according to claim 1, characterized in that (a) when is hydrogen and R2 is hydroxy, that a carbamate ester of the formula where R is a straight-chain or branched alkoxy group with from 1 to 6 carbon atoms, benzyloxy, p-methoxybenzyloxy or 2,4-dimethoxybenzyloxy and Ar is phenyl or p-methoxyphenyl, treated with an excess of acid in an excess of anisole or 1,3-dimethoxybenzene , and when R is different from trimethylsilyloxy, tert-butoxy,'benzyloxy, p-methoxybenzyloxy or 2,4-dimethoxybenzyloxy, that the 3-amino-1,4-cyclohexadiene-carboxylic acid ester derivative thus formed is reacted with tert-butoxy-carbonylimino -2-phenyl-acetonitrile or tert-butyl azidoformate in the presence of a base in a suitable solvent at 25°C for 1-24 hours followed by alkali hydrolysis and then acid hydrolysis, and treatment with base when the free base is desired, or when R is trimethylsilyloxy , tert-butoxy, benzyloxy, p-methoxybenzyloxy or 2,4-dimethoxybenzyloxy, that the 3-benzyloxycarbonylamino-1,5-cyclohexadienecarboxylic acid ester is treated with trifluoroacetic acid in anisole, after which the product is transferred to an ion exchange resin, (b) when R 2 is a straight-chain or branched alkoxy group with from 1 to 8 carbon atoms, that the corresponding derivative in which R 2 is hydroxy, is reacted with an alcohol of the formula R^OH in which R^ is a straight-chain or branched alkyl group with from 1 to 8 carbon atoms, saturated with HCl gas at 25° C for 12 - 36 hours, (c.) when R2 is -NR4R5#at an acid halide or anhydride of the corresponding derivative in which R2 is hydroxy and R-^ has the meaning stated in claim 1, provided that a each free amino group is appropriately protected, is treated with an excess of et amine of the formula HNR^R^ where R4 and R^ have the meanings given in claim 1, in a suitable solvent at 25° C. for 1 to 4 hours, (d) when R2 is that an acid anhydride of the add- corresponding derivative in which R2 is hydroxy and R1 has the meaning specified in Claim x, provided that any free amino group is suitably protected, is reacted with a compound of the structure wherein Rr has the meaning stated in claim 1, and wherein Rg is lower alkyl, in a suitable solvent at 0-50 o C for 1-24 hours, followed by acid and base hydrolysis, (e) when Rx is alkylcarbonyl in which the alkyl part is straight chain or branched and has from 1 to 4 carbon atoms and R2 is hydroxy, that the corresponding derivative in which R-^ is hydrogen is treated with an acid halide of the formula wherein halo is a halogen atom and Rg is a straight or branched chain alkyl group of from 1 to 4 carbon atoms, or a suitable acid anhydride, in water or in dichloromethane in the presence of a base at 0 - 25° C for 1/2 to 24 hours, ( f) when R^ is alkoxycarbonyl in which the alkoxy part is straight-chain or branched and has from 1 to 4 carbon atoms, that the corresponding derivative in which R-^ is hydrogen and R2 is a lower alkoxy group is treated with an alkyl haloformate of the formula wherein halo is a halogen atom and R1Q is a straight or branched chain alkyl group having from 1 to 4 carbon atoms, in water or in dichloromethane in the presence of a base at 0 - 25°C for 1/2 to 6 hours, (g) when R^ is in which R., has the meaning stated in claim 1, that the corresponding derivative where is hydrogen and R2 is a straight-chain or branched net alkoxy group with from 1 to 8 carbon atoms, is treated with an acid of the formula or an anhydride thereof, in which the amino group is suitably protected and R^ has the above meaning in a suitable solvent and in the presence of a dehydrating agent when the free acid is used, at 0 - 35° C for 1 - 12 hours followed by acid and base hydrolysis, and (h) when a pharmaceutically acceptable salt is desired, that the compound thus obtained is reacted with a suitable pharmaceutically acceptable acid or base. 7. Process for producing a compound according to claim 1, characterized in that (a) when is hydrogen and R2 is hydroxy, that a 4-phenylsulfinyl-2-cyclohexenecarboxylic acid ester of the formula in which R is a straight-chain or branched alkoxy group with from 1 to 6 carbon atoms, benzyloxy, p-methoxybenzyloxy or 2,4-dimethoxybenzyloxy, is reacted with silver cyanate in the presence of solid iodine in a suitable solvent at -20 - 25° C for 3 - 24 hours, that the 2-iodo-3-isocyano-4-phenylsulfinylcyclohexanecarboxylic acid ester thus formed is treated with benzyl alcohol or p-methoxybenzyl alcohol, optionally in the presence of a suitable catalyst, forming the corresponding 3-benzyl or 3-p-methoxybenzyl carbamate which is treated with 1 equivalent of a hindered base in a suitable solvent for 1 - 4 hours at 25° C, after which the dehydrodeiodinated derivative thus formed is heated to 60 - 140° C for 1/2 to 24 hours in a suitable solvent during formation of 1,4-diene derivative which is treated with excess acid in excess of anisole or excess of 1,3-dimethoxybenzene, and when R is different from trimethylsilyloxy, tert-butoxy, benzyloxy, p-methoxybenzyloxy or 2,4-dimethoxybenzyloxy, that thus formed 3-amino-1,4-cyclohexadienecarboxylic acid ester derivative is reacted with tert-butoxy-carbonylimino-2-phenylacetonitrile or tert-butylazidoformate in the presence of a base in a suitable solvent at 25°C for 1 - 24 hours, followed by alkali and acid hydrolysis, and treatment with base when the free base is desired, or when R is trimethylsilyloxy, tert-butoxy, benzyloxy, p-methoxybenzyloxy or 2,4-dimethoxybenzyloxy, that the carbamate ester is treated with trifluoroacetic acid followed by an acidic ion exchange resin, (b) when R. is a straight chain or branched alkoxy group with from 1 to 8 carbon atoms, that the corresponding derivative in which R2 is hydroxy, is reacted with an alcohol of the formula R^OH where R^ is a straight-chain or branched alkyl group with from 1 to 8 carbon atoms, saturated with HCl-ga-s at 25° C for 12 - 36 hours, (c) when R2 is -NR^R^, that an acid halide or anhydride of the corresponding derivative in which R2 is hydroxy and R-^ has the meaning stated in claim 1, provided that any free amino group is suitably protected, is treated with an excess of an amine of the formula HNR^R^, in which R^ and R^ have the meanings given in claim 1, in a suitable solvent at 25° C for 1 - 4 hours, (d) when R2s that an acid anhydride of it to corresponding derivative in which R2 is hyroxy and R-^ has the meaning stated in claim 1 provided that any free amino group is suitably protected, is reacted with a compound of the structure wherein Rg is as defined in claim 1, and Rg is lower alkyl, in a suitable solvent at 0-50°C for 1-24 hours, followed by acid and base hydrolysis, (e) when R-^ is alkylcarbonyl and wherein the alkyl moiety is straight chained or branched and has from 1 to 4 carbon atoms and R2 is hydroxy, that the corresponding derivative in which there is hydrogen is treated with an acid halide of the formula wherein halo is a halogen atom and Rg is a straight or branched chain alkyl group having from 1 to 4 carbon atoms, or a suitable acid anhydride, in water in the presence of a base at 0 - 25° C. for 1/2 to 24 hours, (f) when is alkoxycarbonyl in which the alkoxy part is straight-chain or branched and has from 1 to 4 carbon atoms, that the corresponding derivative in which R^ is hydrogen and R2 is a lower alkoxy group is treated with an alkyl haloformate of the formula wherein halo is a halogen atom and R-^q is a straight or branched chain alkyl group having from 1 to 4 carbon atoms, in water or in dichloromethane in the presence of a base at 0 - 25° C for 1/2 hour to 6 hours, ( g) when R-^ is in which R^ has the meaning stated in claim 1, that the corresponding derivative in which R^ is hydrogen and R2 is a straight-chain or branched alkoxy group with from 1 to 8 carbon atoms, is treated with an acid of the formula or an anhydride thereof in which the amino group is suitably protected and R^ has the above meaning, in a suitable solvent in the presence of a dehydrating agent when the free acid is used, at 0 - 35° C for 1 - 12 hours, followed by acid and base hydrolysis , and (h) when a pharmaceutically acceptable salt is desired, that the compound thus obtained is reacted with a suitable pharmaceutically acceptable acid or base.