Total Syntheses of (±)-Deethylibophyllidine Using a Crisscross Annulation: Ring Cleavage of Octahydroindolo[2,3-<i>a</i>]quinolizines Followed by Tandem Cyclizations of Octahydroazecino[5,4-<i>b</i>]indoles
作者:Josep Bonjoch、Joan-Carles Fernàndez、Nativitat Valls
DOI:10.1021/jo980909o
日期:1998.10.1
The total synthesis of (+/-)-deethylibophyllidine (1) is described. Three different sequences provide this pentacyclic alkaloid using a common strategy involving a crisscross annulation. Key steps include (i) C/D ring cleavage of a 2-formyloctahydroindolo[2,3-a]quinolizine to obtain octahydroazecino[5,4-b]indoles, via either a chloroformate induced process or a quaternary ammonium salt formation followed
描述了(+/-)-去乙基核糖胞苷(1)的总合成。三种不同的序列使用涉及十字交叉的通用策略提供了该五环生物碱。关键步骤包括(i)通过氯甲酸酯诱导的过程或季铵盐的形成,将C-D裂解2-甲酰基六氢吲哚并[2,3-a]喹啉用于获得八氢az庚因[5,4-b]吲哚。用锂处理,和(ii)串联过程,该过程由分子内Pictet-Spengler双环化反应组成,该过程在2,3-二取代的吲哚的β-吲哚位置上生成ibophyllidine生物碱的五环骨架的四价螺中心。尝试将该程序扩展到构建(+/-)-ibophyllidine的五环框架会导致非常低的收率。