Abstract: Compounds with neutral endopeptidase (NEP) inhibitory activity corresponding to the formula I ##STR1## in which R.sup.1 is a lower alkoxy-lower-alkyl group whose lower alkoxy radical is substituted by a lower alkoxy group, or a phenyl-lower-alkyl or phenyloxy-lower-alkyl group which can optionally be substituted in the phenyl ring by lower alkyl, lower alkoxy or halogen, or a naphthyl-lower-alkyl group,A is CH.sub.2, O or S,R.sup.2 is hydrogen or halogen,R.sup.3 is hydrogen or halogen,R.sup.4 is hydrogen or a group forming a biolabile ester, andR.sup.5 is hydrogen or a group forming a biolabile ester, and the physiologically acceptable acid addition salts thereof.