54 セスキテルペノイド神経毒、アニサチンの絶対構造と合成研究(口頭発表の部)

概要

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Synthetic studies on anisatin (1), a toxic sesquiterpenoid having a novel B-lactone are described. In order to determine the absolute stereochemistry of anisatin (1) unambiguously, optically active noranisatin (2), an oxidation product of anisatin (1) was synthesized from a bicyclic enone (4) prepared from (R)-(+)-pulegone (3). Spiroalkylation of (4) provided a compound (6), from which a triol (15) was synthesized stereoselectively. The triol (15) was converted into a hydroxy acid (17). Lactonization of (17) followed by oxidation with RuO_4 afforded noranisatin acetonide (19), chiroptical and spectral properties of which were identical with those of the authentic specimen derived from natural anisatin (1) in all respects. Thus, the absolute stereochemistry of anisatin was determined to be depicted as the formula (1). Deprotection of (19) accomplished the synthesis of optically active noranisatin (2). For the synthesis of the natural enantiomer of anisatin (1), an olefin (8) obtained from (4) was transformed into a crossconjugated dienone (25), and subsequently converted into an unsaturated lactone (26), whose structure was established by an X-ray crystallographic analysis. The lactone (26) was further converted into a diacetate (27), from which a triol (28), a key intermediate for the synthesis of optically active anisatin (1) was obtained.
天然有機化合物討論会の論文
1988-09-26