Chiral Dienolate Chemistry in Remote Asymmetric Induction

虽然基于手性助剂的不对称诱导构成了最常用于不对称合成的基本原理，但在手性助剂所赋予的不对称环境之外的位置进行不对称诱导当然是极其困难的。然而，从概念上讲，这个问题可以通过在不对称环境中的不对称诱导过程与不对称传输过程的适当组合来解决，从而实现净远程不对称诱导。为了实现这一概念，我们设计了一种通用的合成方法，该方法依赖于手性二烯醇酯化学进行不对称诱导，然后是不对称传输的信号化过程。研究结果总结如下：(1)手性α、β -或β衍生的二烯醇酯烯丙基化；-不饱和亚胺之后的Cope重排被证明可以影响净远程不对称诱导，从而在高% de的γ位置产生新的手性构型。这种方法的应用在不对称合成zaragozic酸a的C6侧链中得到了证明。(2)二烯酸硼的不对称醛醇反应来源于手性α， β -或β。-不饱和亚胺经硅氧基-柯普重排得到-不饱和亚胺为主要产物。

While the chiral auxiliary-based asymmetric induction constitutes the underlying principle most often utilized for asymmetric synthesis, the asymmetric induction at a position beyond the asymmetric environment imparted by the chiral auxiliary is, of course, extremely difficult. Conceptually, however, this problem could be solved by the proper combination in tandem of an asymmetric induction process within the asymmetric environment with an asymmetric transmission process to effect the net remote asymmetric induction.To realize this concept, we designed a general synthetic approach which relies upon the chiral dienolate chemistry for the asymmetric induction followed by the sigmatropic process for the asymmetric transmission.A summary of the research results is as follow :(1) The allylation of the dienolate derived from the chiral alpha, beta- or beta, gamma-unsaturated imide followed by the Cope rearrangement is shown to effect the net remote asymmetric induction to create a new chirality of either configuration at the gamma-position in high % de. The utility of this approach is shown in the asymmetric synthesis of the C6 side chain of zaragozic acid A.(2) The asymmetric aldol reaction of the boron dienolate derived from chiral alpha, beta- or beta, gamma-unsaturated imide followed by the siloxy-Cope rearrangement is shown to provide the gamma, delta-anti-or-syn-alpha, beta-unsaturated imide as the main product.