Synthesis of the Pentacyclic Skeleton of the Aspidosperma Alkaloids Using Rhodium Carbenoids as Reactive Intermediates
作者:Albert Padwa、Alan T. Price
DOI:10.1021/jo971424n
日期:1998.2.1
derivatives was treated with rhodium(II) acetate. Attack of the amido carbonyl oxygen at the resultant rhodium carbenoid center produced a transient push-pull carbonyl ylide dipole which underwent an intramolecular dipolar cycloaddition reaction. A related annulation sequence was used to prepare the pentacyclic skeleton of the aspidosperma family of alkaloids. Synthesis of the required diazo imide was
用乙酸铑(II)处理由N-烯基取代的3-碳烷氧基-2-哌啶酮衍生物制得的一系列重氮酰胺基酮酯。酰胺基羰基氧在生成的铑类胡萝卜素中心的进攻产生了瞬时的推挽式羰基内酯偶极,该偶极经历了分子内偶极环加成反应。使用相关的环切序列来制备生物碱天冬子精子家族的五环骨架。由3-羧基-3-乙基-2-哌啶酮和N-甲基-3-吲哚乙酸合成所需的重氮酰亚胺。用乙酸铑(II)处理重氮酰亚胺,得到瞬态的1,3-偶极,其随后在吲哚π键上进行环加成。产生的环加合物是相对于偶极的内环加成的结果,其完全符合最低的能量跃迁状态。通过三个步骤将环加合物转化为脱乙酰氧基-4-氧代-6,7-二氢长春花碱。通过X射线晶体学研究确定最终产物的立体化学。