17 オキシラニルアニオンを用いる多環状エーテルの合成研究 : ヘミブレベトキシンBの合成(口頭発表の部)

概要

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Hemibrevetoxin B (1), isolated from cultured cells of the red tide organism Gymnodinium breve, is the smallest member of the polycyclic ether marine toxins and has about half of the skeleton of brevetoxins. Much attention has been paid to the synthesis of 1 owing to its unique structure and strong biological activities and, recently, three total syntheses of hemibrevetxin B have bee reported. We report here a new approach to the synthesis of hemibrevetoxin B based on recent oxiranyl anion methodology developed in our laboratory. The strategy is illustrated by the stereocontrolled synthesis of 2, which is elaborated by sequential coupling of three chiral sulfonyl-stabilized oxiranyl anions 4b, 5b, and 6b to the monocyclic diol 3. The key reactions of our synthesis are alkylation of oxiranyl anions, 6-endo cyclization, and one-carbon ring expansion of a 6-membered cyclic ether to a 7-membered ring by trimethylsilyldiazomethane. These reactions were used in an iterative fashion to synthesize compound 2. Since Yamamoto has already described the conversion of 2 into hemibrevetoxin B, our synthesis of 2 constitutes the formal total synthesis of the natural product.
天然有機化合物討論会の論文
1997-07-20