Preparation of histidine-containing peptides

The process of preparing a di- or polypeptide of the formula ##STR2## wherein R' is hydrogen or methyl and R represents the acyl moiety of an aminoacid or aminoacid chain which, in turn, carries a blocking group at the N-terminus and wherein any functional groups may be protected by carrying a moiety that can be removed chemically without affecting any of the aminoacid links, consisting essentially in stirring His or (3-Me) His with one molar equivalent of an active ester of the aminoacid of formula R-OH in the presence of an inert reaction medium and at least one molar equivalent of triethylamine for at least 1 hour at a temperature below 30.degree. C. and evaporating said reaction medium.