Amphidinolides B4 and B5, Potent Cytotoxic 26-Membered Macrolides from Dinoflagellate Amphidinium Species

Two new cytotoxic 26-membered macrolides, amphidinolides B4 (1) and B5 (2), have been isolated from a marine dinoflagellate Amphidinium sp. (strain Y-100), and the structures were elucidated on the basis of detailed analyses of 2D NMR data including 13C？13C correlations.