Enkephalin degrading enzyme inhibitors

摘要

Compounds which inhibit the brain enzyme degradation of enkephalins and which exhibit their own analgesic effect, having the formula wherein R1 is hydrogen or lower alkyl; X is hydrogen, hydroxy, halo, nitro, amino or lower alkoxy; R2 is hydrogen or wherein R3 is lower alkyl and R4 is L- or D-Thz or Pro, and the pharmaceutically acceptable salts thereof.