(Mercaptopropanoyl)indoline-2-carboxylic Acids and Related Compounds as Potent Angiotensin Converting Enzyme Inhibitors and Antihypertensive Agents

Article abstract of DOI:10.1021/jm00357a014

1-(3-Mercapto-2-methyl-1-oxopropyl)indoline-2-carboxylic acids (7b) and related compounds were synthesized in order to examine their ability to inhibit angiotensin converting enzyme (ACE) and to reduce the systolic blood pressure of spontaneously hypertensive rats (SHR).All four possible stereoisomers of the precursor 1-<3-(benzoylthio)-2-methyl-1-oxopropyl>indoline-2-carboxylic acid (6b) were characterized with absolute stereochemical assigment.The removal of the benzoyl group of the precursor to give 7b was conveniently carried out by treatment with 2-methoxyethylamine.Three of the four stereoisomers of the benzoyl derivative 6 showed in vitro ACE inhibitory activity in the following order: 6b(S,S) > 6b(S,R) > 6b(R,S).The stereoisomer having the R,R configuration was essentialy inactive.The substitution at the C₅ of the indoline nucleus with the Et or OMe group caused only marginal changes in the inhibitory activity.The mercaptan 7b(S,S) was the most active ACE inhibitor synthesized in this study, showing in vitro potency 3 times that of captopril.The augmentation of the potency may be due to the increased hydrophobicity of 7b (S,S) compared with captopril and suggests the presence of a hydrophobic pocket at the active site of ACE.When tested in spontaneously hypertensive rats, 7b(S,S) exhibited oral antihypertensive activity 27 times that of captopril.The corresponding benzoyl derivative 6b(S,S) was 24 times as potent as captopril.The thio lactone 10 obtained by cyclization of 7b(S,S) as a potential prodrug was less potent than the parent compound, 7b(S,S), in the ACE inhibitory and antihypertensive tests.