Research for cyotoxic macrolides for marine dinoflagellates

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1) The absolute stereochemistries in amphidinolide C, E, G, H, T1 - T5, and W, and amphidinolide-H congeners isolated from a marine dinoflagellate Amphidinium sp., were determined on the bases of combination of NMR analyses, degradation experiments, X-ray analysis, and/or synthesis of segments.2) The biosynthetic origins of amphidinolide B, C, G, H, T1, and W were investigated on the basis of ^<13>C NMR data of ^<13>C enriched samples obtained by feeding experiments with [1-^<13>C], [2-^<13>C], and [1,2-^<13>C_2] sodium acetates in cultures of a dinoflagellate Amphidinium sp. These incorporation patterns suggested that these macrolides were generated from successive polyketide chains including isolated C_1 unit from C-2 of acetates, branched C_1 units from C-2 of acetates, "m-m" and/or "m-m-m" units derived only from C-2 of acetates.3) Cytotoxicity of amphidinolides B, D, H, G, H2, H3, H4, H5, G2, and G3 in addition to five derivatives of amphidinolide H was examined, and it was found that the presence of an allyl epoxide, an S-cis-diene moiety, and the ketone at C-20 was important for the cytotoxicity of amphidinolide H-type macrolides.