found to be an excellent coupling reagent having a water-soluble property and a high reactivity; it worked as satisfactory as usual activeesters in regard to the reactivity, product purity, and racemization. The marked advantage of the HODMSP·MeSO4− activeester method was the fact that bifunctional residues such as Arg, Lys, Cys, and Tyr could be selectively acylated when the pH of the reaction mixture