Amphidinins C-F, amphidinolide Q analogues from marine dinoflagellate Amphidinium sp.

Four new polyketides, amphidinins C-F (1-4), have been isolated from the culture broth of symbiotic dinoflagellate Amphidinium sp. The analysis of their spectral data revealed that amphidinins C-F (1-4) were 4,5-seco-analogues of amphidinolide Q (5). The absolute configurations of the new compounds were elucidated by the combination of J-based configuration analysis, modified Mosher's method, and chemical derivatization. Amphidinins D (2) and F (4) are the first glycosides related to amphidinolides. Amphidinins C-F (1-4) showed antimicrobial activity against bacteria and/or fungi.