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Salicylaldehyde ester-induced chemoselective peptide ligations: enabling generation of natural peptidic linkages at the serine/threonine sites.

A serine/threonine-based chemoselective ligation method is described. It uses an O-salicylaldehyde ester at the C-terminus, reacting with N-terminal serine or threonine to realize peptide ligations. The utility of the O-salicylaldehyde ester enables the rapid coupling reaction and the production of an N,O-benzylidene acetal intermediate, which is readily converted into natural peptidic linkages (Xaa-Ser/Thr) at the ligation site.