98(P20) 硫黄の特性を利用した形式的[3+2]付加環化反応によるシクロペンタン合成 : 効率的トリキナン骨格構築法の開発(ポスター発表の部)

概要

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A new synthetic method for cyclopentanone derivatives via formal [3+2] cycloaddition reaction of 2-oxyallyl cation and an olefin was developed. Under the influence of EtAlCl_2 or AlCl_3, allyl acetates 1a, 1b, or 1c reacted with various kinds of olefins to afford 2-(methylthio)cyclopentanone derivatives in good yield. The reaction was highly regioselective to yield the sterically more hindered regioisomer, which indicates that the initial C-C bond formation reaction between an olefin and the (1-(methylthio)-2-siloxy)allyl cation intermediate occurs at the γ-position of sulfur. A new method for methylenecyclopentane annulation via formal [3+2] cycloaddition reaction was also developed by using allylsilane 1d. The reaction proceeds with almost complete regioselectivity as well as high stereoselectivity. An efficient formal total synthesis of triquinane sesquiterpene coriolin was accomplished by using the cyclopentanone annulation reaction. Hydroxyenone 14, which has been reported as a key intermediate in the total synthesis of coriolin, was synthesized as shown in Scheme 5.
天然有機化合物討論会の論文
1996-09-02