1.The hydrobromides of the pentachlorophenyl and 2,4,5-trichlorophenyl esters were synthesized by the carbodiimide method.2.The polymerization of the indicated peptides gave polypeptides of regular structure with the amino acid sequence: [gly-lys(Nɛ-tos)-lys(Nɛ-tos)]n, with a molecular weight of 21,000 in the case of the polymerization of the tripeptide pentachlorophenyl ester, and 7000 in the case of the polymerization of the tripeptide 2,4,5-trichlorophenyl ester (Van Slyke method). Calculation of the molecular weights from the IR spectra gave values of respectively 27,000 and 550