ANTIFUNGAL CYCLODEPSIPEPTIDES, W493-A AND W493-B, FROM FUSARIUM SP - ISOLATION AND STRUCTURAL DETERMIMATION

W493 A and B, which showed strong antifungal activity, were isolated f rom a culture broth of Fusarium sp. The structure of W493 B was determ ined to be that of a cycle clodepsipeptide, S,4R-HMTA-D-allo-Thr-L-Ala -DAla-L-Gln-D-Tyr-L-Ile) (1) by MS and NMR data, an amino acid analysi s, and synthesis of the component. HMTA represents 3-hydroxy-4-methylt etradecanoic acid. W493 A (2) had a similar structure, except that L-n e in 1 was replaced by L-Val. The absolute configuration of each amino acid was determined by chiral HPLC, and the sequence of the component s was determined by HMBC experiments. The sequence of the two alanines was determined to be a L-Ala-D-Ala by a chiral HPLC analysis of the p eptide fragment containing only one Ala residue. The absolute configur ation of HMTA obtained from the hydrolysis of W493 B was determined to be 3S and 4R by comparing with four isomers prepared by enantioselect ive synthesis via Sharpless asymmetric epoxidation.