Glycopeptide ligation via direct aminolysis of selenoester

Direct aminolysis of selenoester in aqueous media was investigated as a glycopeptide ligation strategy. This strategy allows the peptide and glycopeptide ligation to proceed smoothly (even with hindered amino acids) without the need of cysteine residue, N-terminal thiol auxiliary or coupling additive, and to afford the corresponding amide products in excellent yields. No epimerization was observed during ligation reations. In this work, the selenoester of unprotected glycopeptide was readily prepared, and the direct aminolysis of glycopeptide selenoester was successfully applied to synthesize MUC1 mucin sequence efficiently.