Synthetic Studies of Bacitracin. V. Synthesis of Thiazoline Peptides from Cysteine Peptides by Dehydration Procedure

Abstract
Synthesis of thiazoline peptide from cysteine peptide by dehydration with hydrochloric acid in non-aqueous solvent was investigated. By this method, ethyl 2-benzyloxycarbonylaminomethyl-R-Δ2-thiazoline-4-carboxylate and 2 - benzyloxycarbonylaminomethyl-R-Δ2-thiazoline-4-carbonyl-l-leucine ethyl ester were prepared and isolated in pure states. This synthetic method could give a promising route to a total synthesis of bacitracin A. However, the cysteine residue in the latter thiazoline peptide ester was found to be easily racemized under the basic condition.