1977 年 25 巻 11 号 p. 2929-2934
Aromatic ethers, such as anisole or phenetole, were cleaved smoothly with methanesulphonic acid (MSA) or trifluoromethanesulphonic acid in the presence of Met to form methionine-S-methyl (or ethyl) sulphonium salt (I). When the protecting group of Z-Met-OH or Boc-Met-OH was cleaved in the MSA-anisole system, (I) was found as a major product, besides a samll amount of S-benzyl or S-tert-butyl derivative. Thus a Met-containing peptide, H-Tyr-Gly-Gly-Gly-Lys-Met-Gly-OH named endorphin, was synthesized after deprotection of Z (OMe)-Tyr-Gly-Gly-Gly-Lys (Z)-Met (O)-Gly-OH by the MSA-anisole procedure followed by reduction of the Met (O) moiety to the parent amino acid residue with dithiothreitol.