Synthetic Studies of Bacitracin. III. Synthesis of (S)-2-(2-Methylbutyryl)-thiazole-4-carboxylic Acid and Its Peptide Derivative

An optical active 2-(2-methylbutyryl)thiazole-4-carboxylic acid obtained from bacitracin F by an acid hydrolysis was synthesized starting from L-isoleucine. Applying the usual methods for the peptide synthesis, 2-(2-methylbutyryl)thiazole-4-carbonyl-L-leucyl-D-glutamic acid α-methyl-γ-t-butyl ester corresponding to the N-terminal tetrapeptide of bacitracin F, was then synthesized from the thiazole carboxylic acid. UV spectrum of the synthetic tetrapeptide was very similar to that of bacitracin F.