Sudau A, Münch W, Bats J W, Nubbemeyer U
Institut für Chemie, Organische Chemie, Freie Unviersität Berlin, Germany.
Chemistry. 2001 Feb 2;7(3):611-21. doi: 10.1002/1521-3765(20010202)7:3<611::aid-chem611>3.0.co;2-9.
Unsaturated nine-membered ring lactams that contain (E)-olefins within the ring are characterized by planar chiral properties. Thus, selective conversions of the double bond allowed a complete transfer of the planar chiral information into new stereogenic centers The basis of the transformations was the high activation barrier that prevented efficient flipping of the double bond at room temperature (epimerization pR <=> pS) with respect to the ring. Cycloadditions led diastereoselectively to cyclopropano, epimino, epoxy, and dihydroxy azonanones under mild conditions with moderately high yields. The epoxy azonanones were subjected to regio- and diastereoselective transannular epoxide opening/ring contraction sequences to give hydroxy indolizidinones. The regiochemical and stereochemical outcome strongly depends on the configuration of the oxirane and the chiral information of the lactam unit. The so-formed optically active bicycles with defined substitution patterns should serve as versatile building blocks in alkaloid synthesis.
环内含有（E）-烯烃的不饱和九元环内酰胺具有平面手性特性。因此，双键的选择性转化能够将平面手性信息完全转移到新的立体中心。这些转化的基础是存在较高的活化能垒，该能垒在室温下阻止了双键相对于环的有效翻转（差向异构化pR ⇔ pS）。环加成反应在温和条件下以中等较高的产率非对映选择性地生成环丙烷、表亚氨基、环氧和二羟基氮杂环壬酮。环氧氮杂环壬酮经过区域和非对映选择性的跨环环氧化合物开环/环收缩序列反应，得到羟基吲哚里西啶酮。区域化学和立体化学结果强烈取决于环氧乙烷的构型和内酰胺单元的手性信息。如此形成的具有明确取代模式的光学活性双环化合物应可作为生物碱合成中通用的结构单元。
