Developemt of Asymmetric Carbanion Rearrangements with High Stereoselection

该项目的主要成果概述如下。(1)研究了由手性2-恶唑啉衍生的手性氮杂烯醇锂和氮杂烯醇钾的不对称[2，3]-Wittig重排反应。我们发现，这些重排提供了相对较高的光学产率（78- 95%ee）。在这些研究中，我们观察到有趣的影响抗衡阳离子（锂与K）和他们的络合冠醚。此外，该不对称反应已成功地应用于非天然疣卡琳内酯的手性合成。(2)研究了脯氨醇和缬氨醇衍生的酰胺体系中手性酰胺Li-和Zr（）-烯醇末端的不对称[2，3]-Wittig重排<IV>反应。不幸的是，已发现这些不对称变体仅提供中等水平的不对称诱导。然而，有趣的是，Zr-烯醇化物变体已经显示出与Li-烯醇化物相反的非对映选择意义。 ...更多信息 对应物。(3)详细研究了8-苯基薄荷醇衍生的手性酯体系中手性酯烯醇化物末端的不对称[2，3]-Wittig重排反应。首先，我们已经发现Li-烯醇化物重排提供了极高的光学产率（&gt; 95%ee）沿着高的赤型选择性（&gt;90%）。因此，这种类型的不对称重排提供了一个有效的方法，手性合成<alpha>-羟基-<beta>-烷基羧酸衍生物。它的效率已被证明在疣卡内酯的简单手性合成。第二，<IV><IV>已发现涉及由甲硅烷基烯醇醚通过金属转移生成的Ti（）-和Sn（）-烯醇化物的重排表现出非常低水平的不对称诱导。第三，<IV>Li-烯醇化物通过金属转移反应生成Zr（Ⅱ）-烯醇化物，与Li-烯醇化物相比，Zr（Ⅱ）-烯醇化物的重排反应提供了较高的光学产率，在此基础上，我们讨论并阐明了[2，3]-Wittig重排反应中金属烯醇化物的结构。少

The main results of this project are summarized as follows.(1) Asymmetric [2,3]-Wittig rearrangement involving chiral lithium and potassium azaenolate termini generated from chiral 2-oxazolines have been investigated. We found that these rearrangements provided relatively high optical yields (78-95% ee). During these studies, we have observed interesting influences of the countercation (Li vs. K) and their complexation with a crown ether. Furthermore, the asymmetric reaction has successfully been applied to the chiral synthesis of unnatural verrucarinolactone.(2) Asymmetric [2,3]-Wittig rearrangement involving chiral amide Li- and Zr( <IV> )-enolate termini generated from the prolinol- and valinol-derived amide systems has been studied. Unfortunately, these asymmetric variants have been found to provide only moderate levels of asymmetric induction. Interestingly, however, the Zr-enolate variant has been shown to the opposite sense of diastereofacial selection to that of the Li-enolate … More counterpart.(3) Asymmetric [2,3]-Wittig rearrangement involving chiral ester enolate termini generated from the 8-phenylmenthol-derived chiral ester system has been investigated in details. First, we have found that the Li-enolate rearrangement provides an extremely high optical yields (>95% ee) along with a high erythro-selectivity (>90%). Thus, this type of asymmetric rearrangement offers an efficient method for chiral synthesis of <alpha> -hydroxy- <beta> -alkyl carboxylic acid derivatives. Its efficiency has been demonstrated within the simple chiral synthesis of verrucarinolactone. Second, the rearrangement involving Ti( <IV> )- and Sn( <IV> )-enolates generated from the silyl enol ether via transmetalation has been found to exhibit very low levels of asymmetric induction. Third, the rearrangement involving Zr( <IV> )-enolate generated from the Li-enolate via transmetalation, by contrast, provides a high optical yield comparable to that of the Li-enolate counterpart.On the basis of these results described above, we have discussed and elucidated the structures of the metal enolates involved in the [2,3]-Wittig rearrangements. Less