Desymmetrization of a Centrosymmetric Diepoxide: Efficient Synthesis of a Key Intermediate in a Total Synthesis of Hemibrevetoxin B
作者:Joanne M. Holland、Mark Lewis、Adam Nelson
DOI:10.1021/jo026456b
日期:2003.2.1
The preparation of an established intermediate in a total synthesis of hemibrevetoxin B is described. The acid-catalyzed cyclization of trans-4,5-epoxyoctane-2,7-dione exhibited a valuable mixture of kinetic and thermodynamic control: stereospecific epoxide opening was followed by equilibration of the products to provide the required trans-fused octahydropyrano[3,2-b]pyran ring system. Two-directional
描述了在半短毒素B的全合成中已建立的中间体的制备。反式-4,5-环氧辛烷-2,7-二酮的酸催化环化反应显示出动力学和热力学控制的有价值的混合物:开环立体有择环氧化物,然后平衡产物以提供所需的反式稠合八氢吡喃[3, 2-b]吡喃环系统。通过缩醛取代,臭氧分解和硫叶立德介导的环氧化作用进行的双向精细加工提供了中心对称的二环氧化合物。合成的关键步骤是天然产物合成中的中心对称分子的首次去对称化:Jacobsen不对称环氧化物的水解和丙酮化在两个步骤中提供了97%的收率和> 95%ee的已知合成中间体。