Epoxide-Initiated Cationic Cyclization of Azides: A Novel Method for the Stereoselective Construction of 5-Hydroxymethyl Azabicyclic Compounds and Application in the Stereo- and Enantioselective Total Synthesis of (+)- and (−)-Indolizidine 167B and 209D
作者:P. Ganapati Reddy、Sundarababu Baskaran
DOI:10.1021/jo035258x
日期:2004.4.1
and seven-membered epoxyazides 3b,c underwent smooth cyclization to give 5-hydroxymethyl azepine 4b and 5-hydroxymethyl azocine 4c, respectively, as a single detectable diastereomer. This novel methodology was elegantly applied in the stereoselective total synthesis of indolizidine alkaloids 167B and 209D. Further, the enantioselective total synthesis of natural and unnatural indolizidine alkaloids 167B
基于环氧化物引发的叠氮化物的阳离子环化,已开发出一种新颖且通用的方法用于5-羟甲基氮杂双环骨架的立体选择性构建。系统地研究了模型化合物3-(1-氧杂-螺[2.4]庚-4-基)丙基叠氮化物3a的关键环化反应,发现EtAlCl 2是理想的催化剂。使用不同的环尺寸进一步测试了该转化的一般性,其中六元和七元环氧叠氮化物3b,c进行了平滑环化,得到了5-羟甲基氮杂b 4b和5-羟甲基偶氮cine呤4c分别作为单个可检测的非对映异构体。该新方法巧妙地应用于吲哚并立定生物碱167B和209D的立体选择性全合成中。此外,通过使用Sharpless不对称二羟基化作为关键步骤,完成了天然和非天然吲哚并立定生物碱167B和209D的对映选择性全合成。