Antibiotics from gliding bacteria, 85([not equivalent to]) - Melithiazols A-N: New antifungal beta-methoxyacrylates from myxobacteria

From cultures of Melittangium lichenicola, Archangium gephyra and Myxococcu s stipitatus, thirteen new beta-methoxyacrylate (MOA) fungicides related to myxothiazols (1) have been isolated. Melithiazols A (2a), D (2b), K (2c), and L (2d) are characterized by a thiazoline-thiazole system, whereas melit hiazols B (3a), E (3b), F (3c), G (3d), H (3e), I (3f), M (3g), and N (3h) are bis(thiazoles). Melithiazol C (4), as the first representative of this class of compounds, contains only one thiazole ring. The structures were es tablished on the basis of spectroscopic data, and confirmed in the case of melithiazol E (3b), including its relative configuration,by an X-ray struct ure analysis. The absolute configuration of melithiazols A (2a) and B (3a) was determined by degradation and CD spectroscopy. Antifungal and cytotoxic activities, inhibition of NADH oxidation, and lipophilicities of melithiaz ols 2-4, myxothiazols 1, and strobilurin-type compounds are compared.