Investigations of Cascade Cyclizations of Terpenoid Polyalkenes via Radical Cations. A Biomimetic-type Synthesis of (±)-3-Hydroxy-spongian-16-one
作者:Martin Demuth、Frank Goeller、Christoph Heinemann
DOI:10.1055/s-2001-15074
日期:——
A short and efficient synthesis of the tetracyclic oxygenated diterpene analog of 8, i. e., of 3-hydroxy-spongian-16-one (7), has been achieved in only five steps via a cascade cyclization of the functionalized terpenoid polyalkene 4. Photoinduced electron transfer serves as the pivotal step for selectively creating a radical cation intermediate. Such polycyclizations are radical-driven upon regio- and stereoselective trapping of the radical cation by a nucleophile, such as water in the present case. The overall reaction sequence mimics the non-oxidative biosynthesis of terpenes.
一个简短高效的合成8的四环氧化二萜类物质的合成,即3-羟基-海绵烯-16-酮(7),只需通过对功能化单萜多烯4进行级联环化反应完成,仅用五步。光诱导电子转移是选择性生成自由基阳离子中间体的关键步骤。这种多环化反应是在自由基阳离子被亲核试剂(如本例中的水)进行区域和立体选择性捕获的过程中受到自由基驱动的。整体反应序列模拟了单萜的非氧化生物合成。