The present invention relates to 4-(aminomethyl) cyclohexane-l-carboxylic acid derivatives, to their preparation and to pharmaceutical compositions containing them.

The present invention provides 4-[N-(3',4'-methylenedioxybenzylidene)aminomethyl]cyclohexane-l-carboxylic acid, which is a compound represented by the formula (I):

or a C_l-C₄ alkyl ester thereof or a pharmaceutically acceptable salt thereof, such as the sodium salt or ammonium salt. The cyclohexane ring may be present in the trans-or cis-forms or in a mixture thereof. The compounds of the invention exhibit a low toxicity in mammals and can be used in the treatment of inflammation, thrombosis, hypertension, asthma, cancer, rheumatism or systemic lupus erythematosus.

The compounds of the invention are preferably prepared by reacting 3,4-methylenedioxybenzaldehyde, which is a compound of formula (II):

with a 4-aminomethyl-cyclohexane-l-carboxylic acid or an ester thereof represented by the formula (III):

wherein the cyclohexane ring may be in the trans- or cis- form or in a mixture of trans- and cis-forms and X represents hydrogen or an alkyl group of from 1 to 4 carbon atoms, and optionally converting the resulting compound into a pharmaceutically acceptable salt.

The reaction between the compound of the formula (II) and the compound of the formula (III) is a dehydration- condensation reaction and is preferably carried out in an organic solvent at not higher than 150°C, preferably at a temperature of from 0 to 120°C under an atmosphere of an inert gas. At higher than 150°C, the yield of the desired product is reduced because of various side reactions. Any organic solvent may be used provided it does not participate in the reaction. A lower alcohol such as methanol or ethanol; benzene; toluene; dimethylformamide; acetonitrile or the like can be employed.

Since the reaction takes place with dehydration, the reaction is preferably carried out in the presence of a dehydrating agent or while removing water formed by the reaction under the reflux of the solvent. An anhydrous lower alcohol such as anhydrous methanol or ethanol can be used as the solvent and at the same time as the dehydrating agent.

The compound of the invention (acid- or ester form) can be isolated by treating the resulting reaction mixture by a known method. The salt form can be prepared by the conventional neutralization method using a base such as hydroxide, carbonate or bicarbonate of an alkali or alkaline earth metal, for example, sodium, potassium, calcium or magnesium, or ammonia or a primary-, secondary-or tertiary amine or a quaternary ammonium salt. For example, a sodium salt can be obtained by neutralizing the compound of the invention (an acid form) obtained by the above-mentioned reaction with an alcoholic- or aqueous solution of sodium hydroxide under an inert gas atmosphere at lower than 100°C, usually at 0 to 50°C.

The compounds of the invention show an inhibitory effect on platelet aggregation and/or polynuclear leukocyte migration, and a low acute toxicity, as will be shown in Example 5 below. Accordingly, the compounds of the invention are useful as a remedy for various diseases, such as inflammation, thrombosis, hypertension, asthma or cancer, and especially for chronic diseases such as rheumatism or systemic lupus erythematosus (SLE) When used for pharmaceutical purposes, the salt or ester must be pharmaceutically acceptable.

The present invention further provides a pharmaceutical composition which comprises as active ingredient a compound of formula (I) or a C_l - C₄ alkyl ester thereof or a pharmaceutically acceptable salt thereof, together with a pharmaceutically acceptable carrier or diluent.

The compound of the invention can be administered perorally, rectally or by injection in various dosage forms as a composition together with a pharmaceutically acceptable carrier or diluent. The composition can be in unit dosage form, containing a therapeutically effective amount of a compound of the invention. Conventional pharmaceutical adjuvants may be present. Two or more of the compounds of the invention and/or other pharmaceutically active materials may be present in the pharmaceutical composition.

The composition may be in the form of a tablet, sublingual tablet, powder, capsule, troch, aqueous or oily solution, suspension, emulsion, syrup, aqueous or oily injection. Examples of the carrier or diluent mentioned above include water, gelatin, lactose, starch, pectin, magnesium stearate, stearic acid, talc, vegetable oil, gum arabic, polyalkylene glycol, vaseline, sorbitan trioleate, polyoxyethylene-sorbitan mono-oleate, alkylphenol, aliphatic alcohols and polyvinyl pyrrolidone. In the composition, if necessary, an edulcorant, flavouring agent, tinctorial agent, preservative, salt for osmoregu- lation or buffer, that is a conventional pharmaceutical adjuvant, may be present.

The content of a compound of the invention in the pharmaceutical composition may be varied, for example, from 0.01% to less than 100% by weight of the composition preferably 0.05% - 80% by weight of the composition.

The pharmaceutical composition of the invention can be administered to a human or animal parenterally, for example, rectally, by injection (hypodermic, intramuscular or intravenous, or drip), also preferably perorally (for example sublingual etc.).

A dose of the pharmaceutical composition of the invention is typically 0.1 to 500 mg, preferably 0.5 to 200 mg, per day per kilogram of body weight in the case of peroral administration to a human, and 0.01 to 200 mg, preferably 0.1 to 100 mg, in the case of parenteral administration. The dose can be administered in from one to four portions a day. However, the dose depends on age, individuality, condition of a disease, etc. of the human or animal patient, and may therefore be outside the above-mentioned range.

The method for preparation, properties and pharmacological effects of compounds of the invention are illustrated in the following Examples. Reference is made in the Examples to the accompanying drawings in which:

• Figure 1 shows aninfrared absorption spectrum of sodium 4-[N-(3',4'-methylenedioxybenzylidene)aminomethyl] cyclohexane-l-carboxylate taken using a KBr tablet;
• Figure 2 shows an infrared absorption spectrum of methyl 4-[N-(3¹,4^1-methylenedioxybenzylidene)aminomethyl] cyclohexane-l-carboxylate taken using a KBr tablet; and
• Figure 3 shows an infrared absorption spectrum of ethyl 4-[N-(3',4'-methylenedioxybenzylidene)aminomethyl] cyclohexane-l-carboxylate taken using a KBr tablet.

Example 1

Preparation of 4-rN-(3¹,4^1-methylenedioxybenzylidene)-aminomethyl]cyclohexane-1-carboxylic acid:

1.91 Grams (12.72 mmol) of 3,4-methylenedioxybenzaldehyde was dissolved in 30ml of dehydrated and purified methanol. The resulting solution was added dropwise into 2.00 g (12.72 mmol) of trans-4-aminomethyl-cyclohexane-l-carboxylic acid under an atmosphere of nitrogen. The resulting mixed solution was refluxed with stirring for 3 hours.

Small amounts of insoluble materials were removed by filtration. The filtrate was concentrated and left overnight at room temperature. Educing crystals were collected by filtration, washed with methanol and vacuum dried. 1.22 Grams of 4-[N-(3¹,4^1-methylenedioxybenzylidene) aminomethyl]-cyclohexane-l-carboxylic acid melting at 146 to l47°C (according to hot plate method) was obtained. The yield was 33.2%.

The characteristics of this compound of the invention thus obtained were as follows:

• (1) Elementary analytical follows:

  • Found(%) C: 66.30, H: 6.70, N: 4.90
  • ^Calcd.(%) as C₁₆H₁₉O₄N, C: 66.42, H: 6.62, N: 4.84

• (2) NMR: δ = 1.03~1.90 (9H, m), 1.99~2.13(1H), 3.36(2H, d), 6.06(2H, s), 6.95(lH, d), 7.19(lH, d), 7.28(lH, s) and 8.15(1H, s).

Example 2

Preparation of sodium 4-rN-(3',4'-methylenedioxybenzylidene)-aminomethyl]cyclohexane-1-carboxylate:

2.893 Grams (10.0 m mol) of 4-[N-(3',4'-methylenedioxybenzylidene)aminomethyl]cyclohexane-l-carboxylic acid obtained in Example 1 was added under an atmosphere of nitrogen into 100 ml (10.0 m mol) of 0.1 N aqueous solution of sodium hydroxide. The resulting mixture was stirred for 2 hours at room temperature to obtain a yellow solution. The yellow solution was filtered and then freeze-dried. 3.472 Grams of sodium 4-[N-(3',4'-methylenedioxybenzylidene) aminomethyl]cyclohexane-l-carboxylate were obtained. The yield was 100%.

The characteristics of the sodium salt thus obtained were as follows:

• (1) Melting point (according to capillary method): 270.0 to 273.0°C (decomposed)
• (2) Elementary analytical data:

• • Found (%) C: 55.60, H: 6.20, N: 4.10
  • Calcd.(%) as
  • ^C₁₆^H₁₈^N0₄.^Na.2H₂0 C: 55.32, H: 6.38, N: 4.03

• (3) Infrared absorption spectrum (KBr Tablet): as shown in Figure 1 of the accompanying drawings.

Example 3

Preparation of methyl 4-[N-(3',4'-methylenedioxy- benzlidene)-aminomethyl]cyclohexane-1-carboxylate:

(a) After dropping 12.5 g of thionyl chloride into 82 ml of icewater-cooled methanol while stirring well, the cooling bath for methanol was removed, and then after adding 11.0 g of trans-4-aminomethylcyclohexane-l-carboxylic acid to the mixture, the thus formed mixture was heated for 5 hours at 50 to 60°C. Then, the reaction mixture was filtered while warm. The filtrate was concentrated to about 25 ml under a reduced pressure. The crystals educed on adding 140 ml of ether to the concentrated solution were collected by filtration after icewater- cooling and recrystallized from a mixture of methanol and ether to obtain 13.4 g of coulourless plate-like crystals of methyl trans-4-aminomethylcyclohexane-l-carboxylate hydrochloride in a yield of 92.1% and giving the following elementary analytical data:

Elementary analytical data:

• Found (%) C: 51.70, H: 9.00, N: 6.80
• Calcd. (%) as C₉H₁₈NO₂Cl C: 52.04, H: 8.74, N: 6.74

(b) After neutralizing 4.43 g of the thus obtained methyl trans-4-aminomethylcyclohexane-l-carboxylate hydrochloride with 20 ml of 1N sodium hydroxide solution, the solution was extracted three times with 30 ml portions of ethyl acetate. The extract after washing with water was dried with anhydrous sodium sulfate, and the solvent in the filtrate obtained by filtration of the dried extract was removed by evaporation under a reduced pressure in a warm water bath to obtain 2.70 g of a colourless liquid of methyl trans-4-aminomethylcyclohexane-l-carboxylate in a yield of 78.9% and giving the following elementary analytical data:

Elementary analytical data:

• Found (%) C: 62.90, H: 10.10, N: 7.90
• Calcd.(%) as C₉H₁₇NO₂ C: 63.12, H: 10.01, N: 8.18

(c) After dissolving 1.60 g (9.34 m mol) of the thus obtained methyl ester and 1.40 g (9.34 m mol) of piperonal into 40 ml of methanol, the solution was refluxed for 16 hours. Then, after removing the solvent from the solution under a reduced pressure in a warm water bath, the residue was dissolved in 40 ml of n-hexane. After filtering the solution while warm, the filtrate was subjected to recrystallization to obtain 2.68 g of colourless acicular crystals of methyl 4-[N-(3',4'-methylenedioxybenzylidene)-aminomethyl]cyclohexane-1-carboxylate in a yield of 94.7%, melting at 55.0 to 58.0°C (according to capillary method) and giving the following elementary analytical data and the infrared absorption spectrum as follows:

(1) Elementary analytical data:

• Found(%) C: 67.20, H: 7.10, N: 4.60
• Calcd.(%) as C₁₇H₂₁NO₄ C: 67.31, H: 6.98, N: 4.62

(2) Infrared absorption spectrum (KBr Tablet): as shown in Figure 2 of the accompanying drawings.

Example 4

Preparation of ethyl 4-[N-(3',4'-methylenedioxybenzylidene)-aminomethyllcyclohexane-l-carboxylate

In a similar manner to Example 3, except for using ethanol instead of methanol, ethyl trans-4-aminomethylcyclohexane-1-carboxylate hydrochloride, ethyl trans-4-aminomethylcyclohexane-l-carboxylate and ethyl 4-[N-(3',4'-methylenedioxybenzylidene)-aminomethyl] cyclohexane-1-carboxylate were synthesized in that order.

The respective physical properties of the products are as follows:

• (a) Ethyl trans-4-aminomethylcyclohexane-l-carboxylate hydrochloride:

  • Yield: 14.2 g (91.6%)
  • Melting point (according to capillary method): 187 ~ 188°C

Elementary analytical data:

• Found(%) C: 54.20, H: 9.10, N: 6.40
• Calcd.(%) as
• C₁₀H₂₀NO₂C_l C: 54.16; H: 9.09; N: 6.3₂
• (b) Ethyl trans-4-aminomethylcyclohexane-l-carboxylate:

  • Yield: 3.10 g (83.8%) Elementary analytical data:

    • Found(%) C: 64.80, H: 10.00 N: 7.80
    • Calcd.(%) as
    • C₁₀H₁₉NO₂ C: 64.83, H: 10.34; _N: 7.56

• (c) Ethyl 4-[N-(3',4'-methylenedioxybenzylidene)aminomethyl]-cyclohexane-l-carboxylate;

  • (1) Yield: 2.63 g (83.0%)
  • (2) Melting point: 72.5~73.5°C (according to capillary method)
  • (3) Elementary analytical data:

    • Found(%) C: 68.20, H: 7.30, N: 4.40
    • Calcd.(%) as
    • C₁₈H₂₃NO₄ C: 68.12, H: 7.30, N: 4.41

  • (4) Infrared absorption spectrum (KBr Tablet): as shown in Figure 3 of the accompanying drawings.

Example 5

Tests for inhibition of blood platelet actarectation and for acute toxicity of sodium 4-rN-3',4'-methylenedioxybenzylidene)-aminomethyllcyclohexane-l-carboxylate:

5-1) Test for inhibition of platelet aggregation was carried out while using rabbit's platelets, an aqueous physiological saline solution of sodium 4-[N-(3',4'-methylenedioxybenzylidene) aminomethyl]cyclohexane-1-carboxylate and 400 micromols of sodium arachidonate as the aggregation agent in a platelet aggregation tracer PAT 4A (made by Niko Bioscience Company, Japan) as the testing apparatus. The percent (%) inhibition of aggregation of the platelets by sodium arachidonate due to sodium 4-[N-(3',4'-methylenedioxybenzylidene)aminomethyl]-cyclohexane-1-carboxylate at concentrations of 500, 1000 and 1500 micromols were found to be 30, 75 and 100, respectively.

5-2) Acute oral toxicity test was carried out by orally administering aqueous solutions of sodium 4-[N-(3',4'-methylene-dioxybenzylidene)aminomethyl]cyclohexane-1-carboxylate to groups of female JCL-ICR mice five weeks after their birth. No abnormalities were found on the mice to which 3000 mg/kg of the test compound was administered.

Example 6

Tests for inhibition of the migration of polymorphonuclear leukocytes to the inflammatory region:

Tests for the inhibition of the migration of polymorphonuclear leukocytes to the inflammatory region due to sodium 4-[N-(3',4'-methylenedioxybenzylidene) aminomethyl]cyclohexane-l-carboxylate were carried out following the Granuloma-CMC-Pouch method (refer to Ishikawa et al. J. Pharmaceut. Soc, Jap., Vol. 88, page 1472, 1968). Namely, after cutting the hair off a region of the back of male rats (Donryu, body weight: 150 g), 5 ml of air was injected subcutaneously in that region and, further, 5 ml of an aqueous 2% (W/V) solution of sodium carboxymethyl cellulose (CMC) at 37°C was injected. Sodium 4-[N-(3',4'-methylenedioxybenzylidene)aminomethyl]cyclohexane-l-carboxylate was orally administered to one rat as a solution in aqueous physiological saline solution at a dose of 100 mg/kg at the time of injecting the solution of CMC, whilst 1 mg/kg of indomethancin was orally administered to another rat at the time of injecting the solution of CMC.

Specimens of the liquid (0.5 ml, each) which had effused into the pouch were collected 3,6 and 24 hours after the 2% CMC solution had been injected. The number of polymorphonuclear leukocytes in each specimen was counted after staining to determine the rate of inhibition of migration of the polymorpholeukocytesas compared to the number of the polymorpholeukocytes in a specimen collected from a control animal to which only the aqueous CMC solution was injected after the air. The results are shown in the Table below.