Synthetic Studies on Bacitracin. VII. Isomerization of Amino Acid Components of Thiazoline Peptides

Abstract

Abstract Ethyl 2-(1-benzyloxycarbonylaminoethyl)-R-Δ2-thiazoline-4-carboxylate (III), ethyl 2-(1-benzyloxycarbonylamino-2-methyl-n-butyl)-R-Δ2-thiazoline-4-carboxylate (VI) and their acid amide derivatives (V, VII and VIII) were prepared by either the iminoether coupling method or the dehydration method. As a general character of thiazoline peptide, it was found that the amino acid residue connected to thiazoline ring at N-terminal side is completely racemized at the stage of thiazoline ring formation, and further epimerized, in the case of isoleucine, by treatment with the basic reagent.