Synthesis of (R)-(−)-phoracantholide I based on stereocontrolled cleavage of internal acetal
作者:Shinji Nagumo、Hiroshi Suemune、Kiyoshi Sakai
DOI:10.1016/s0040-4020(01)89442-4
日期:——
prepared from 9 underwent silica-gel catalyzed, facile ring cleavage in a stereocontrolled fashion to afford the ring-enlarged 9-nonanolide derivatives (18). This methodology was applied for the synthesis of (R)-(−)-phoracantholide I. Examination using the Dreiding stereomodel provides a rationalized explanation for the stereocontrolled cleavage.
用MCPBA氧化(S)-2-丁烯基-2-乙氧基羰基环己酮(6),直接得到两个手性内缩醛1S,6S,9R-(8)和1R,6S,9S-(9),而不是环氧化物。通过用BF 3醚化物处理,由9获得的叔醇(12)通过逆醛醇缩合反应和内部缩醛的重建产生了意外的产物(14),并且没有获得预期的裂解产物(3)。由9制备的仲醇(15b)的甲磺酸酯以立体控制的方式进行了硅胶催化的,容易的开环裂解,得到了扩环的9-壬醇衍生物(18)。该方法学被用于(R)-(-)-佛花苷I的合成。使用Dreiding立体模型的检查为立体控制的裂解提供了合理的解释。