P-58 渦鞭毛藻Amphidinium sp.由来の奇数員環マクロリドの三次元構造解析および生合成研究(ポスター発表の部)

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During our studies on bioactive substances from Okinawan marine organisms, we have investigated extracts of the laboratory-cultured marine dinoflagellate Amphidinium sp., which was a symbiont of the Okinawan marine flatworm Amphiscolops sp., to isolate a series of cytotoxic macrolides, named amphidinolides, with various backbone-skeletons and biogenetically unusual structural features. Here we describe isolation and structure elucidation of two novel 15-membered macrolides, amphidinolides O (1) and P (2), which were obtained by further examination of the cytotoxic fraction of the extract of this microalga and exhibited cytotoxicity. Compounds 1 and 2 possess closely related structures; the C-11 ketone group of the former is replaced by an exomethylene group for the latter. Both 1 and 2 have 7 chiral centers; the relative configurations of five of them located on a dihydropyran and an epoxide moiety (C-3, C-4, C-7, C-8, and C-9) were elucidated by the NMR data (coupling constants and NOESY correlations), while the remaining two positions (C-14 and C-15) were suggested as 14R^* and 15R^* based on comparison of the ^1H NMR data and the calculation results of confomational searching. The biosynthetic origin of amphidinolide J (3) was investigated by means of feeding experiments of labeled [1-^<13>C], [2-^<13>C], and [1,2-^<13>C_2] sodium acetate into the culture of the dinoflagellate Amphidinium sp. It was revealed that all carbons of amphidinolide J (3) were derived from acetates, and the backbone of 3 was suggested to consist of unusual mixed polyketides involving dicarboxylic acids such as succinate or α-ketoglutarate, and one-carbon branches were derived from the C-2 of acetate. Since the carbons constituting the 15-membered lactone ring of 3 were not constructed from the sequential normal polyketide chain, the generation of the unusual odd-numbered lactone ring may be justified to be allowable.
天然有機化合物討論会の論文
1995-09-01

P-58 渦鞭毛藻Amphidinium sp.由来の奇数員環マクロリドの三次元構造解析および生合成研究(ポスター発表の部)

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