Oxo-ester Mediated Native Chemical Ligation: Concept and Applications

A direct oxo-ester peptide ligation method has been developed. Through the use of an activated C-terminal para nitrophenyl ester (1), it is possible to achieve direct cysteine ligations (1 + 2 -> 4). Peptide substrates incorporating bulky C-terminal amino acids (1) can be accommodated with high reaction efficiency.