A member of the class of isoquinolines that is (3S)-2-L-alanyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid in which the alpha-amino group of the alanyl residue has been substituted by a 1-ethoxycarbonyl-4-phenylbutan-2-yl group (the all-S isomer). A prodrug for quinaprilat (by hydrolysis of the ethyl ester to the corresponding carboxylic acid), it is used as an angiotensin-converting enzyme inhibitor (ACE inhibitor) used (generally as the hydrochloride salt) for the treatment of hypertension and congestive heart failure.