Ultrasound accelerated conversion of Nα-urethane protected peptide esters to their thiopeptides using P2S5

A fast and efficient synthesis of Nα-protected thiopeptide esters from the corresponding peptide esters using P2S5 as thionating agent assisted by ultrasonication has been described. The conversion of peptide bond into thioamide was complete in 20–40 min at rt. The reaction was accomplished without using any base. The products isolated were characterized using 1H NMR, 13C NMR and mass spectroscopy.