38 イェッソトキシンの合成研究(口頭発表の部)

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Yessotoxin (YTX, 1), which belongs to the ladder-shaped polyether family, has been isolated from the digestive glands of the scallops in association with diarrhatic shellfish poisoning. The toxin turned out later to be produced by dinoflagelate Pritocaratium sp., and further transferred and accumulated through the food chain. YTX is recently reported to be a modulator of cytosolic calcium levels of human lymphocytes and a caspase activator. Its broad spectrum of biological activities and unique arched molecular structure have therefore attracted the attention of synthetic chemists. During the course of our synthetic studies, we have developed an efficient method for the convergent synthesis of polycyclic ethers via α-cyano ethers, which was successfully applied to the synthesis of the FGHIJ-ring fragment (18) of YTX. Unification of the F-ring diol (6) and IJ-ring aldehyde (7) through acetal formation, followed by the regioselective cleavage of the acetal afforded the α-cyanoether (9). Construction of the GH ring was achieved by using ring-closing metathesis and reductive etherification. A novel method for synthesizing the ABC-ring fragment (30) of YTX has been also developed. Coupling of the A-ring triflate (19) and 2-lithiofuran (20) followed by oxidative ring expansion of the furan gave the six membered-ring enone (22). Construction of the BC ring system was achieved by means of intramolecular oxy-Michael addition and reductive etherification. Furthermore, construction of the K-ring was achieved by enyne cross metathesis reaction of alkyne (33) with β-methallylalcohol, and subsequent 6-exo cyclization of the vinylepoxide (35) with CSA. Further studies directed towards total synthesis of YTX based on our convergent strategy will be also reported.
天然有機化合物討論会の論文
2006-09-15

38 イェッソトキシンの合成研究(口頭発表の部)

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