Amino−Zinc−Enolate Carbometalation Reactions: Application to Ring Closure of Terminally Substituted Olefin for the Asymmetric Synthesis of <i>cis</i>- and <i>trans</i>-3-Prolinoleucine
作者:Philippe Karoyan、Jean Quancard、Jacqueline Vaissermann、Gérard Chassaing
DOI:10.1021/jo026535n
日期:2003.3.1
The reaction is stereospecific, leading to a trans-3-substituted proline derivative, whereas a cis stereochemistry was observed with the amino-zinc-enolate cyclization of terminally nonsubstituted olefins. Absolute configurations obtained for the 3-prolinoleucine were established by X-ray analysis, NMR, and optical activity comparison of the cis and trans derivatives obtained by an unambiguous pathway
氨基锌烯醇盐环化反应是3-取代脯氨酸合成的直接途径。作为经典的分子内碳金属化反应,将锌加成至双键的适用性限于其中末端烯烃碳未被取代的底物。对合成顺式和反式3-脯氨酰亮氨酸衍生物感兴趣,以进行结构-活性关系(SAR)研究,我们集中精力通过末端取代的双键的氨基-锌-烯酸酯环化制备这些化合物。本文中我们报道活化基团例如环丙基与末端烯烃碳的连接使得末端取代的烯烃的氨基-锌-烯醇酸酯环化。反应是立体特异性的,导致反式3取代的脯氨酸衍生物,而在末端未取代的烯烃的氨基-锌-烯醇酸酯环化中观察到顺式立体化学。通过X射线分析,NMR和通过明确途径获得的顺式和反式衍生物的光学活性比较,确定了3-脯氨酰亮氨酸的绝对构型。