Abstract: The invention relates to novel peptide derivatives, their preparation process and their pharmaceutical use.These derivatives are in accordance with the following formula: ##STR1## in which A stands for hydrogen, a radical derived from an amino acid, a group of formula DE in which D represents the N-t-butyloxycarbonyl (BOC), tertamyl-oxycarbonyl (tAOC), N-benzyloxycarbonyl, N-benzoyl, N-acetyl, N-pivaloyl, N-carbamoyl, or N-succinyl radical, and E stands for a single bond or a radical derived from an amino acid which is either not substituted or substituted by HSO.sub.3 or a peptide formed from 2 to 5 amino acids, either unsubstituted or substituted by HSO.sub.3 ; B represents the L-methyonyl, D-methionyl, L-norleucyl, D-nodeucyl, L-leucyl, D-leucyl, L-norvalyl or D-norvalvyl radical; Y represents H, CH.sub.2 OH, COOR.sup.1 with R.sup.1 representing hydrogen or an allyl radical in C.sub.1 and C.sub.4 or CO--NHR.sup.2 with R.sup.2 representing hydrogen, an alkyl radical in C.sub.1 and C.sub.4 or NH.sub.