CYSTOTHIAZOLE-A AND CYSTOTHIAZOLE-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 myxoba cterium, Cystobacter fuscus. The gross structures of these compounds w ere elucidated by spectroscopic analysis, and their absolute stereoche mistry was determined by chemical degradation of cystothiazole A. Cyst othiazole A inhibits fungi and human tumor cells, whereas it is inacti ve against bacteria. The antifungal activity appears to result from th e inhibition of submitochondrial NADH oxidation. Although these compou nds are structurally related to the known antibiotic myxothiazol, cyst othiazole A was more active against fungi and less cytotoxic than myxo thiazol.