Patent GB-1156930-A (GB)
Title: Improvements in or relating to Tetrahydrobenzimidazole Compounds
IPC: C07D235/16
Filed: 1966-12-13
Abstract: 1,156,930. Substituted 1,3-imidazoles. SYNTEX CORP. 13 Dec., 1966 [18 Dec., 1965], No. 55724/66. Heading C2C. Novel substituted 1,3-imidazoles of the general formula. wherein R is H, an alkyl group containing less than 8 carbon atoms, a substituted or unsubstituted aryl, aralkyl or alkaryl group, a monocyclic heterocyclic group containing less than 9 carbon atoms, a carboalkoxy group containing less than 8 carbon atoms or wherein R<SP>5</SP> is H or an alkyl, aryl, alkaryl, aralkyl, monocyclic heterocyclic or carboalkoxy group as above defined, R<SP>6</SP> is H or an alkyl, aryl, aralkyl or alkaryl group as above defined and each of R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP> and R<SP>4</SP> may be H, or an alkyl, aryl, aralkyl or alkaryl group as above defined provided that at least two of R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP> and R<SP>4</SP> are H and when one of R<SP>1</SP> and R<SP>4</SP> is other than H the other is H, are prepared, when R is other than the above-mentioned amido-carboxylic group, by heating an N-(2-isonitrosocyclohexan-1-one-3-ylidene) alpha amino acid derivative of the formula wherein M is H or an alkali metal, dissolved in an inert organic solvent to a temperature of at least 40‹ C. provided that, when M is an alkali metal, the reaction is carried out in the presence of approximately one molar equivalent per mole of isonitroso compound of a strong acid or, when R is an amido-carboxylic group, by a similar method using a compound of the general formula wherein R' is H or an alkyl, aryl, aralkyl or alkaryl group as above defined. The first-mentioned isonitroso starting material may be prepared using the following reaction scheme: wherein X is halogen having an atomic number greater than 9, M is H or alkali metal and R<SP>61</SP> is an alkyl, aryl, aralkyl or alkaryl group as above defined. The cyclic diketone is condensed with the amino acid ester hydrohalide in the presence of sufficient base to convert the hydrohalide to the free amino group, and the resulting N- (cycloalk - 2 - en - 1 - one - 3 - yl) alpha - amino - acid ester is converted to the corresponding free acid, e.g. by basic hydrolysis or, when it is a benzyl ester, by selective hydrogenolysis. The free acid is then converted to the required isonitroso starting material or its alkali metal salt by treatment with nitrous acid or nitrosyl chloride. The isonitroso starting material required to give a product in which R is an amidocarboxylic group is prepared using the following reaction scheme wherein R<SP>7</SP> is H, alkyl, aryl, aralkyl or alkaryl as above defined or an alkali metal, by reacting a cyclic diketone with a peptide ester hydrohalide to yield the peptide ester which may also be prepared by reacting a suitable alpha-amino acid with an amino acid ester hydrohalide. The ester can then be reacted with nitrous acid or nitrosyl chloride to give the isonitroso compound or the ester may be de-esterified to the free carboxy compound before treatment, in which case R<SP>7</SP> can be hydrogen. Pharmaceutical compositions comprise as active ingredient a novel compound of the invention and a pharmaceutically acceptable excipient. The compositions have hypotensive, antiinflammatory and sedative activity and may be administered orally or by injection.