Active esters in the formation of ester bonds between amino acids and polymeric supports

The imidazole catalyzed transesterification of active esters was used for the formation of the ester bond between the carboxyl group of protected amino acids and the hydroxyl group of a polymeric support applied in solid phase peptide synthesis. Anchoring of the C-terminal residue to the hydroxymethyl polymer proceeded smoothyl and provided a high degree of incorporation. No racemization was observed in the imidazole-catalyzed alcholysis. The procedure could be carried out with various active esters such as esters of o-and p-nitrophenol, 2,4,5-trichlorophenol, pentachlorophenol and N-hydroxysuccinimide.