An Efficient Approach to <i>Aspidosperma </i>Alkaloids via [4 + 2] Cycloadditions of Aminosiloxydienes: Stereocontrolled Total Synthesis of (±)-Tabersonine. Gram-Scale Catalytic Asymmetric Syntheses of (+)-Tabersonine and (+)-16-Methoxytabersonine. Asymmetric Syntheses of (+)-Aspidospermidine and (−)-Quebrachamine
作者:Sergey A. Kozmin、Tetsuo Iwama、Yong Huang、Viresh H. Rawal
DOI:10.1021/ja017863s
日期:2002.5.1
readily adapted to the asymmetric synthesis of these compounds. The strategy is demonstrated by the total synthesis of (+/-)-tabersonine (rac-1), proceeding through a 12-step sequence. The basis for this approach was provided by a highly regio- and stereoselective [4 + 2] cycloaddition of 2-ethylacrolein with 1-amino-3-siloxydiene developed in our laboratory. Subsequent elaboration of the initial adduct
描述了一种简洁、高度立体控制的吲哚生物碱 Aspidosperma 家族的策略,该策略很容易适应这些化合物的不对称合成。该策略由 (+/-)-tabersonine (rac-1) 的全合成证明,通过 12 步序列进行。这种方法的基础是我们实验室开发的 2-乙基丙烯醛与 1-氨基-3-甲硅烷氧基二烯的高度区域和立体选择性 [4 + 2] 环加成。随后通过闭环烯烃复分解反应有效地将初始加合物加工成六氢喹啉 DE 环系统。开发了烯醇甲硅烷基醚与(邻硝基苯基)苯基碘氟化物的新型邻硝基苯基化,以实现必要的吲哚部分的有效区域选择性引入。ABDE四环最终高产转化为五环目标rac-1依赖于分子内吲哚烷基化和区域选择性C-碳甲氧基化。我们的方法在战略上与以前的路线不同,并且包含访问 Aspidosperma 吲哚生物碱家族的许多其他成员所必需的内置灵活性。通过以下 Aspidosperma 生物碱的不对称