1.The possiblity of using 2,4, 5-trichlorophenyl esters for synthesis of polypeptides of regular structure has been demonstrated.2.In their “polymerizing” ability the 2,4, 5-trichlorophenyl esters yield only to pentachlorophenyl esters.3.Polypeptides of regular structure have been synthesized, with the sequences glycine-prolineglycine, glycine-hydroxyproline-hydroxyproline, and glycine-proline-hydroxyproline; these are models of the collagen structure.4.The corresponding glycylhydroxyprolylhydroxyproline ester is proposed as a convenient monomer which permits comparing different polymerization meth