Promoting Effect of Pentamethylbenzene on the Deprotection of O-Benzyltyrosine and N^ε-Benzyloxycarbonyllysine with Trifluoroacetic Acid

Abstract

Ο-Benzyltyrosine was rapidly deprotected without formation of 3-benzyltyrosine by treatment with trifluoroacetic acid containing pentamethylbenzene. This method was also found to be useful in the deprotection of N^ε-benzyloxycarbonyllysine [Lys (Z)] and N^G-4-methoxy-2, 3, 6-trimethylbenzenesulfonylarginine [Arg (Mtr)]. The new deprotecting method was successfully applied to the synthesis of kyotorphin (Tyr-Arg).