New cyclic depsipeptide antibiotics, clavariopsins A and B, produced by an aquatic hyphomycetes, Clavariopsis aquatica. 2. Structure analysis.

The structures of new cyclic decadepsipeptides, clavariopsins A and B, were determined to be cyclo[-(R)-2-hydroxyisovaleryl-L-pipecoyl-L-MeVal-L-Val-L-MeAsp-L-MeIle-L-MeIle-Gly L-MeVal-L-Tyr(OMe)-] and cyclo[-(R)-2-hydroxyisovaleryl-L-pipecolyl-L-Val-L-Val-L-MeAsp-L-Melle-L-MeIle-Gly-L-MeVal-L-Tyr(OMe)-], respectively, by spectroscopic analyses, especially using 2D NMR techniques. The absolute stereochemistry was elucidated by the advanced Marfey's method and chiral HPLC analysis.

Cystothiazoles A and B, new bithiazole-type antibiotics from the myxobacterium Cystobacter fuscus.

New bithiazole-type antibiotics, cystothiazoles A (C20H26N2O4S2) and B (C20H26N2O5S2), have been isolated from a culture broth of the myxobacterium, Cystobacter fuscus. The gross structures of these compounds were elucidated by spectroscopic analysis, and their absolute stereochemistry was determined by chemical degradation of cystothiazole A. Cystothiazole A inhibits fungi and human tumor cells, whereas it is inactive against bacteria. The antifungal activity appears to result from the inhibition of submitochondrial NADH oxidation. Although these compounds are structurally related to the known antibiotic myxothiazol, cystothiazole A was more active against fungi and less cytotoxic than myxothiazol.