<i>N</i>‑Sulfanylethyl­aminooxy­butyramide (SEAoxy): A Crypto-Thioester Compatible with Fmoc Solid-Phase Peptide Synthesis

An <i>N</i>-sulfanylethyl­amino­oxy­butyramide (SEAoxy) has been developed as a novel thioester equivalent for native chemical ligation. SEAoxy peptide was straightforwardly synthesized by conventional Fmoc solid-phase peptide synthesis without a problem. Moreover, SEAoxy peptide could be directly applied to native chemical ligation owing to the intramolecular <i>N</i>-to-<i>S</i> acyl shift that releases the peptide-thioester <i>in situ</i>. This methodology was successfully applied to the synthesis of two bioactive peptides