Stereoselective Total Syntheses of the Racemic Form and the Natural Enantiomer of the Marine Alkaloid Lepadiformine via a Novel <i>N</i>-Acyliminium Ion/Allylsilane Spirocyclization Strategy
作者:Pu Sun、Cuixiang Sun、Steven M. Weinreb
DOI:10.1021/jo0201070
日期:2002.6.1
subsequent protection of the primary alcohol gave amino acetal 27. The synthesis was concluded from 27 by a four-step procedure: acid-catalyzed ring closure, amino nitrile formation, introduction of the hexyl chain by a Grignard reaction to an iminium salt, and removal of the O-benzyl protecting group to give (+/-)-lepadiformine (6). The enantioselective total synthesis of 6 started from known optically
三环海洋生物碱lepadiformine(6)的外消旋形式和天然对映异构体的立体选择性总合成已使用新型N-酰基亚胺离子与烯丙基硅烷的分子内螺环化形成A / C环作为关键步骤完成。使用我们的基于氧化自由基的邻氨基苯甲酰胺远程官能化方法,然后通过铜催化将格氏试剂16加到衍生自N的N-酰亚胺离子中间体上,在外消旋螺环11的C-13处引入羟甲基15.随后将硅烷17进行Tamoo氧化,得到所需的羟甲基化合物19,其通过加氢甲酰化然后进行醛保护而转化为二甲基乙缩醛25。水解25的苯甲酰胺部分,然后保护伯醇,得到氨基缩醛27。该合成是通过以下四个步骤从27合成的:酸催化的闭环,氨基腈形成,格氏试剂引入己基链反应生成亚胺盐,并除去O-苄基保护基,得到(+/-)-lepadiformine(6)。6的对映选择性总合成从已知的光学纯溴化物37开始,该溴化物衍生自(S)-焦谷氨酸,并遵循类似的序列,涉及N-酰基