O-to-O Acyl Transfer for Epimerization-free Peptide C-terminal Salicylaldehyde Ester Synthesis

Peptide salicylaldehyde esters are the requisite coupling partner in Ser/Thr ligation reactions towards chemical protein synthesis.In general, it would be cost-effective and efficient to use side chain protected peptide acids, after Fmoc-solid phase peptide synthesis, for direct C-terminal derivatization, however this has yet to be achieved, due to an intrinsic epimerization pathway.Here, we report the development of 2-(dichloromethyl)phenol (DCP) as a reagent which can directly form peptide salicylaldehyde esters in an epimerization-free manner.The peptide salicylaldehyde ester reaction products have been applied in the convergent total chemical synthesis of linker histone H1.2 using sequential Ser/Thr ligation reactions.