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.
