Selective Cleavage of tert-Butyloxycarbonyl Protecting Group with Dilute Organic Sulfonic Acid without Decomposition of Tryptophan Residue

Abstract

The reagent of 2 M anhydrous p-toluenesulfonic acid in dioxane containing 2% anisole cleaves selectively tert-butyloxycarbonyl group in Boc-Trp-OH without any detectable decomposition of tryptophan residue. Another reagents such as dilute p-toluenesulfonic acid, methanesulfonic acid or ethanesulfonic acid in acetic acid and methanesulfonic acid or ethanesulfonic acid in dioxane, which are containing 2% anisole and 2% 1, 2-ethanedithiol or triphenylphosphine as reducing reagent, have also similar properties to those of p-toluenesulfonic acid in dioxane containing 2% anisole. The utility of the reagents was proved as applied to the syntheses of three kinds of tryptophan containing peptide derivatives by the classical solution method.