Peptide Thioesters for SPPS

Significance

Peptide thioesters are key molecules for native chemical ligation (NCL) in the preparation of peptides. However, the standard Fmoc-based SPPS protocol is not applicable for the preparation of peptide thioesters, because the thioester group is cleavable under the Fmoc deprotection conditions using piperidine. The authors reported the first Fmoc-based preparation of peptide thioesters using tert-butyl thioester as a linker. Four varieties of pentapeptide thioesters 6a-d were prepared in 67-86% yield via protected peptides 4 by the standard Fmoc chemistry.