P-1 ビスセンブラノイド類メチルサルコフィトエートの合成研究(ポスター発表の部)

概要

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Methyl sarcophytoate (1) and four other compounds belong to biscembranoids (tetraterpenoids). Biogenetically, they are considered to be formed by Diels-Alder (D-A) reaction of two cembranes. Since the intermolecular D-A reactions of large membered-ring diene-dienophile pairs have never been reported, we investigated the D-A reaction of the 14-membered diene-dienophile pair, 4 and 5, both of which are the model compounds for the intact units, 2 and 3, of 1. Furthermore, the total synthesis of the hitherto unknown diene unit 3 of 1 have been achieved. The model dienophile 4 was prepared from cyclododecanone in eight steps and the model diene 5 was prepared from 4 in five steps. Under the thermal D-A conditions, all four possible adducts were produced, among which the adduct 6, having the same cyclohexene configuration as natural biscembranoids, was the major product. In contrast, under the Lewis acid-promoted D-A conditions, only the unnatural regioisomers 7 and 9 were produced. The hitherto unknown diene unit 3 was synthesized as follows. The important acyclic precursor 29 was prepared from geraniol by Sharpless asymmetric epoxydation, aldol reaction, Michael-type 6-endo-trig tetrahydropyranone formation, regioselective epoxydation as the key steps. The Kodama-Ito cyclization of 29 gave the 14-membered product, which was transformed to 3 by the 4-step sequence.
天然有機化合物討論会の論文
1995-09-01