Total Syntheses of (+)-Echinopine A and B: Determination of Absolute Stereochemistry
作者:Thomas Magauer、Johann Mulzer、Konrad Tiefenbacher
DOI:10.1021/ol902263k
日期:2009.11.19
The first total syntheses of the novel 3,5,5,7-sesquiterpenoids (+)-Echinopine A (1) and B (2) were achieved. Thereby the proposed structures were confirmed, and the absolute stereochemistry was determined. The key features are (1) the stereoselective installation of the vinyl-moiety on the concave side of the bicyclo[3.3.0]octane core via Myers’ [3,3]-sigmatropic rearrangement, (2) the finding that
首次新颖的3,5,5,7-倍半萜(+)-Echinopine A(1)和B(2)的总合成。从而证实了所提出的结构,并确定了绝对立体化学。主要特征是(1)通过Myers的[3,3]-σ重排将乙烯基部分立体选择性地安装在双环[3.3.0]辛烷核的凹入侧,(2)发现取代基在在基本条件下,可以将酮旁边的C7位置差向至所需的凹面,(3)通过RCM关闭高度应变的七元环,以及(4)乙烯基三氟甲磺酸酯与乙烯酮的不寻常的C2同源性甲硅烷基乙缩醛。