An efficient peptide ligation using azido-protected peptides via the thioester method

Azido-protected Fmoc-Lys-OH (Fmoc-Lys(N-3)-OH) was synthesized from Fmoc-Lys-OH by the copper(II)-catalyzed diazo transfer method, and introduced to a peptide by the ordinary Fmoc-based solid-phase peptide synthesis. This azido peptide could be condensed with a peptide thioester by the Ag+-free thioester method without any significant side reactions. The azido group was easily reduced to an amino group by Zn powder after peptide condensation. (C) 2008 Elsevier Ltd. All rights reserved.