Neomangicols:: Structures and absolute stereochemistries of unprecedented halogenated sesterterpenes from a marine fungus of the genus Fusarium

Three novel sesterterpenes, neomangicols A-C (1-3) were isolated from the mycelial extract of a marine fungus belonging within the genus Fusarium. The carbon skeleton of the neomangicols is undescribed and constitutes a new class of C-25 rearranged sesterterpenes. The structures of the new metabolites were determined by 1D and 2D NMR methods, and the absolute configuration of 3 was determined by Mosher ester analysis of a diacetonide derivative. The configurations of the three stereocenters in the side-chain were assigned on the basis of molecular modeling and NOESY NMR correlations observed for several diacetonide derivatives of 3. Neomangicols A and B are cytotoxic against HCT-116 human colon carcinoma in in vitro evaluation, while neomangicol B inhibits the growth of the Gram-positive bacterium Bacillus subtilus with a potency similar to that of the antibiotic gentamycin.