Chemical Research Laboratory, Sankyo Co., Ltd., Hiromachi, Shinagawa-ku, Tokyo 140, Japan. Received April 13, 1987 c~-[6-[[(S)-l-(Ethoxycarbonyl)-3-phenylpropyl] amino]-5- oxoperhydro-l, 4-thiazepin-4-yl] acetic acids (monoester monoacids) and their dicarboxylic acids having the hydrophobic substituents at the 2-or 3-position of the thiazepinone ring were prepared and assayed for angiotensin-converting enzyme (ACE) inhibitory activity. ...