The compounds of the general Formula (I), wherein R1 is aryl or alkyl; R2 represents alkyl; R3 represents alkyl or aralkyl, are valuable pharmaceutical intermediates, which can be prepared by reacting a compound of the general Formula (IV) (wherein the definitions of R1 and R2 are as above), with at least 2 molar equivalents of the compound of the general Formula (VI) (wherein X represents halogen or tertiary butyloxycarbonyloxy group and R3 is as defined above). The known compounds of the general Formula (II) (wherein R1 and R2 are as defined above) are prepared by reacting the compounds of the general Formula (I) with thionyl chloride. The compounds of the general Formula (I) are new intermediates useful in the synthesis of pharmaceutically active ingredients, particularly in the preparation of ACE-inhibitors, e.g. enalapril, perindopril or ramipril.