Improved Solid-Phase Synthesis of Tryptophan-Containing Peptides. I. Use of Hydrogen Chloride in Formic Acid as a Reagent for the Cleavage of t-Butyloxycarbonyl Group

Abstract
An improved method has been described for the solid-phase synthesis of tryptophan-containing peptides. Hydrogen chloride in formic acid has been introduced as a reagent for the cleavage of the t-butyloxycarbonyl group owing to the stableness of tryptophan and Ni-formyltryptophan in this system. The effectiveness of the new reagent has been demonstrated in the synthesis of the tryptophan-containing heptapeptide, lysylalanylglycyl-leucylglycyltryptophylleucine.