The present invention relates to specific inhibitors of the cysteine protease dipeptidyl peptidase I (DP I)which can be used in the treatment of malignant cell degeneration, immune diseases impaired wound healing and metabolic diseases of humans and are represented by the general formula ##STR00001## and the pharmaceutical salts thereof, in which R is a peptide or a branched or unbranched C.sub.1 C.sub.9 alkyl chain, a branched or unbranched C.sub.2 C.sub.9 alkenyl chain, a branched or unbranched C.sub.2 C.sub.9 alkynyl chain, a C.sub.3 C.sub.9 cycloalkyl, C.sub.4 C.sub.9 carbocyclic, C.sub.5 C.sub.14 aryl, C.sub.3 C.sub.9 heteroaryl, C.sub.3 C.sub.9 heterocyclic, all of the above residues optionally being substituted, the residue AS--AS is a dipeptide or a mimetic thereof, AS is an amino acid or a peptide mimetic thereof. The amino acid is peptide bound with R and R' is a branched or unbranched C.sub.1 C.sub.9 alkyl chain, a branched or unbranched C.sub.2 C.sub.9 alkenyl chain, a branched or unbranched C.sub.2 C.sub.9 alkynyl chain, a C.sub.3 C.sub.9 cycloalkyl, C.sub.4 C.sub.9 cycloalkenyl, C.sub.2 C.sub.9 heterocycloalkyl, C.sub.3 C.sub.9 heterocycloalkenyl, C.sub.5 C.sub.14 aryl, C.sub.3 C.sub.9 heteroaryl, C.sub.3 C.sub.9 heterocyclic, whereas the heterocycloalkyl, heterocycloalkenyl, heteroaryl, heterocyclic residue can have up to 6 hetero ring atoms, an amino acid or a peptide mimetic thereof, all of the above residues may be optionally substituted, or is H.