Formation of peptide thioamides by use of Fmoc amino monothioacids and PyBOP.
摘要:
Endothiopeptides have been obtained by using PyBOP(R) promoted coupling between Fmoc-protected amino monothioacids and amino acid or peptide esters. The protected endothiopeptides (Fmoc-Gly-psi(CSNH)-Phe-OEt, Fmoc-Tyr(Bu(t))-psi(CSNH)-Gly-Gly-Phe-Leu-OBu(t) and (Fmoc-Gln(Trt)-psi(CSNH)-Phe-OEt) were formed (55, 45 and 37% yield) in admixture with the corresponding oxopeptides, from which they were easily separated chromatographically. Preliminary racemisation studies indicate that products of high optical purity are obtained. The mechanism for endothiopeptide formation is briefly discussed.