Abstract: In an amino acid having .omega.-amino group protected with a protective group or a peptide having the residue of such a protected amino acid, the improvement according to which the protective group is p-methylbenzylsulfonyl group. The .omega.-amino acids protected with p-methylbenzylsulfonyl or the peptides having residues of such protected amino acids are useful for production of various peptides by liquid phase method as well as by solid-phase method, because the protective group has specific selectivity of remaining stable under the conditions commonly employed in the removal of .alpha.-aminoprotecting group but is cleaved smoothly in a good yield by hydrogen fluoride without exerting untoward unfluences upon peptides.

Abstract: A novel method for removal of protective group(s) from an amino acid or peptide having thiol group(s) protected with p-methoxybenzyl, 1-adamantyl or t-butyl group by treating the protected amino acid or peptide with the mercuric salt of acetic acid or halogenoacetic acid, the removal being effected selectively and very smoothly in a good yield under extremely mild conditions without giving any undesirable influence upon other functional or protective group(s).