Development of Serine/Threonine Ligation and its Applications

Abstract

In addition to the prevalently successful native chemical ligation (NCL) in protein chemical synthesis, Ser/Thr ligation (STL) represents another genre of chemoselective ligation strategy that directly makes use of N-terminal Ser/Thr residues within native proteins. The design lies in the reaction between one peptide fragment bearing N-terminal Ser/Thr and another fragment carrying C-terminal salicylaldehyde ester. Through aldehyde capture and O-to-N acyl transfer, followed by acidolytic cleavage of the acetal intermediate, the native peptidic bond is formed. To date, STL has found versatile applications in total synthesis of various bioactive peptides and proteins in both linear and cyclic forms, including human erythrocyte acylphosphatase, mucin-1 glycopeptide, and antibiotic daptomycin. Expectedly, STL would provide a useful addition to the toolbox of protein chemical synthesis.