Bioactive macrolides and polyketides from marine dinoflagellates

Absolute stereochemistry of amphidinolides G and H, potent cytotoxic 27- and 26-membered macrolides, respectively, isolated from a marine dinofiagellate Amphidinium sp., was determined by X-ray diffraction analysis, synthesis of a degradation product, and chemical interconversion. Six new macrolides, amphidinolides H2∼H5, G2, G3, and W, have been isolated from a marine dinoflagellate Amphidinium sp. (strain Y-42), and the structures were elucidated by 2D NMR data and chemical means. The structure-activity relationship of amphidinolide H-type macrolides for cytotoxicity was examined. The biosynthetic origins of amphidinolides B, C, H, J, T1, and W were investigated on the basis of ¹³C NMR data of ¹³C-enriched samples obtained by feeding experiments with [1-¹³C], [2-¹³C], and [1,2-¹³C₂] sodium acetates in cultures of the dinoflagellates. Five novel long-chain polyhydroxyl compounds, colopsinols A∼E, were obtained from the Amphidinium sp. (strain Y-5).