Iriomoteolides-9a and 11a: two new odd-numbered macrolides from the marine dinoflagellate Amphidinium species.

Iriomoteolides-9a (1) and 11a (2), new 15- and 19-membered macrolides, respectively, have been isolated from the marine dinoflagellate Amphidinium species (strain KCA09052). Compounds 1 and 2 were obtained from the extracts of the algal cells inoculated in the PES and TKF seawater medium, respectively. The structures of 1 and 2 were assigned on the basis of detailed NMR analyses. Compounds 1 and 2 exhibited cytotoxic activity against human cervix adenocarcinoma HeLa cells.