Going Round in Circles with N→S Acyl Transfer

Abstract

It is not highly sophisticated, yet the N→S acyl transfer reaction of a native peptide sequence potentially fills an important technology gap. While several routes to synthetic peptide thioesters exist, only one is routinely applicable for biologically derived samples. Using the naturally occurring amino acid cysteine as the sole activator for N→S acyl transfer we have demonstrated transformation of synthetic and biologically derived precursors into thioesters for use in Native Chemical Ligation, providing a viable alternative for biological samples. Further refinement will be key to realising the full potential of this intriguing process, and increase the number of applications in peptide engineering and therapeutics.1 Introduction2 N→S acyl transfer in ‘normal’ peptide sequences3 Reduced reactivity of internal Xaa-Cys motifs as an advantage in head-to-tail peptide cyclisation4 Reduced reactivity of internal Xaa-Cys motifs as an advantage in modification and cyclisation of biologically produced precursors5 Hydrazinolysis of Xaa-Cys motifs and the acyl hydrazide as a stable thioester equivalent6 Rapid thioester formation via an N→Se acyl shift7 Outlook and conclusions