Amide derivatives

Tripeptide amides of the formula and salts thereof, wherein P is H or an alkylthio or aralkylthio radical, m is an integer from 1-4' and R1 is H or an alkyl or aryl radical, provided that when m is 2 and R1 is H, then P is not methylthio, are prepared by reacting an amino acid derivative of the formula wherein X is a porotecting group with an a -L-aspartyl-L-phenylalanine amide of the formula where R2 is H, a hydrogenolysable radical or an alkyl radical such that the group COOR2 may be hydrolysed to -COOH under mildly acidic conditions, or a salt thereof, followed by replacement of X and, if present, the group R2 by H. The 2,4,5 - trichlorophenyl esters of N-benzyloxycarbonyl L-norleucine, L-norvaline, L-a -amino butyric acid and of N-t-butoxycarbonyl L-ethionine are prepared.