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Microbial enantioselective ester hydrolysis for the preparation of optically active (3R,5S)-(-)-5-phenyl-4,1-benzoxazepine-3-acetic acid derivatives as potent squalene synthase inhibitors was investigated. Pseudomonas diminuta and Pseudomonas taetrolens hydrolyzed the racemic ethyl ester of the 5-(2-chlorophenyl) analogue to yield the (-)-carboxylic acid with excellent enantiomeric excess (99% ee). We found that the (-)-enantiomer was an active inhibitor. Bulkiness of the ester moiety did not affect the enantioselectivity but did affect reactivity. The racemic ethyl ester of the 5-(2-methoxyphenyl) analogue, 5-(2,3-dimethoxyphenyl) analogue and 5-(2,4-dimethoxyphenyl) analogue were also hydrolyzed with Pseudomonas taetrolens to afford enantiomerically pure (-)-carboxylic acids in large scale. As another route to (3R,5S)-(-)-7-chloro-5-(2,3-dimethoxyphenyl)-1-neopentyl-2-oxo-1,2,3,5-tetrahydro-4,1-benzoxazepine-3-acetic acid [(-)-1c], the earlier intermediate (-)-2-amino-5-chloro-alpha-(2,3-dimethoxyphenyl)benzyl alcohol [(-)-12] was successfully obtained by asymmetric hydrolysis of (+/-)-5-chloro-alpha-(2,3-dimethoxyphenyl)-2-pivaloylaminobenzyl acetate with Pseudomonas sp. S-13 with99% ee in kilogram scale followed by alkaline treatment. The product (-)-12 was converted to (-)-1c without racemization.

A seires of (R)-3-amino-4-oxo-2, 3, 4, 5-tetrahydro-1, 5-benzothiazepine-5-acetic acids (8) and (S)-3-amino-4-oxo-2, 3, 4, 5-tetrahydro-1, 5-benzoxazepine-5-acetic acids (9) having an (S)-1-carboxy-ω-(4-piperidyl)alkyl group on the amino group at the 3-position was prepared as part of a search for long-acting inhibitors of the angiotensin converting enzyme (ACE). The length (n) of the carbon chain in the piperidylalkyl moiety was varied from two six in order to determine the optimal structure. The most prolonged activity in vivo was observed with (R)-3-[(S)-1-carboxy-5-(4-piperidyl)pentyl]amino-4-oxo-2, 3, 4, 5-tetrahydro-1, 5-benzothiazepine-5-acetic acid (8c : CV-5975) on i.v. and p.o. administrations.

A chemoenzymatic synthesis of the new angiotensin converting enzyme inhibitor CV-5975 (1) is described. The optically active key intermediate for the synthesis of 1, ethyl (R) -6- (1-benzyloxycarbonyl-4-piperidyl) -2-hydroxyhexanoate ((R) -4), was prepared by kinetic resolution of the racemic α-hydroxyester ((RS) -4) with a lipase and also by asymmetric reduction of the α-oxoester (3) with baker's yeast. The enantiomeric excess (ee) of the α-hydroxyester ((R) -4) produced by these enzymatic procedures exceeded 60%. This optically active alcohol ((R) -4) was converted to its mesylate ((R) -5), which was then subjected to SN2 reaction with the aminobenzothiazepine derivative (2) followed by deprotection to yield 1.