cycloadduct in high yield. The formation of the bicyclic isoxazolidine arises from conjugate addition of the oxime onto the diene to give a transient nitrone that spontaneously undergoes an intramolecular dipolar cycloaddition. The resulting cycloadduct derived from the cascade sequence was converted into (±)-cylindricine C by: (1) a reductive-cyclization to set the BC-ring skeleton, (2) a base-induced cyclization
描述了一种有效的立体控制的途径来合成(±)-cylindricineC。9-羟基非-1-en-5-酮
肟与2,3-双(苯磺酰基)-
1,3-丁二烯的反应以高收率提供了7-氧杂-1-氮杂降
冰片烷环加合物。双环
异恶唑烷的形成是由于将
肟共轭加成到二烯上而得到的瞬态硝酮,该瞬态硝酮自发地经历了分子内偶极环加成反应。通过以下方式将所得的级联序列衍生的环加合物转化为(±)-cylindricine C:(1)还原环化以设置BC环骨架;(2)碱诱导的环化以构建
三环核心;和( 3)正己基侧链的氧化-共轭加成以完成合成。