Ophiocerins A−D and Ophioceric Acid:  Tetrahydropyran Derivatives and an Africane Sesquiterpenoid from the Freshwater Aquatic Fungus Ophioceras venezuelense

Four new tetrahydropyran derivatives called ophiocerins A−D (1−4) and a new africane sesquiterpenoid (ophioceric acid; 5) have been isolated from cultures of the aquatic fungus Ophioceras venezuelense, together with the known compound regiolone. The structures and relative stereochemistry of these compounds were determined by analysis of 1D and 2D NMR data, while absolute stereochemical assignments for 1−4 were proposed by application of the exciton chirality CD method.