Further structure-activity relationships of the myxobacterial antibiotics cystothiazoles

Eight derivatives of the bithiazole-type myxobacterial antibiotic cystothiazole A were evaluated for antifungal activity against a phytopathogenic microorganism for a further structure-activity relationship. Two of them, an acetate and a fully conjugated non-chiral derivative, were new derivatives obtained by chemical derivatization of cystothiazole C. The results confirmed the importance of the bend conformation at C-4/C-5, the methyl ether at C-5, and the lipophilicity of the terminal alkyl group of the molecule.