In the so-called thioester method for the condensation of peptide segments, protectinggroups for amino and thiolgroups are required for chemoselective ligation. In this study, we developed a novelthiolprotectinggroup, N-methyl-phenacyloxycarbamidomethyl (Pocam). We used it for protection of cysteine side chains, and synthesized Pocam-containing peptides and peptide thioesters. These were condensed