Department of Chemistry, Seoul National University, Gwanak-1 Gwanak-ro, Gwanak-gu, Seoul, 151-742, South Korea.
Angew Chem Int Ed Engl. 2017 Sep 25;56(40):12250-12254. doi: 10.1002/anie.201705713. Epub 2017 Aug 24.
An asymmetric pathway to the caged tetracyclic pyrrolidine alkaloid, dendrobine, is reported. The successful synthetic strategy features a one-pot, sequential palladium-catalyzed enyne cycloisomerization and rhodium-catalyzed diene-assisted pyrrolidine formation by allylic CH activation. The developed transition-metal-catalyzed cascade process permits rapid access to the dendrobine core structure and circumvents the handling of labile intermediates. An intramolecular aldol condensation under carefully defined reaction conditions takes place with a concomitant detosylation, followed by reductive amine methylation, to afford a late-stage intermediate (previously identified by several prior dendrobine syntheses) in only 10 synthetic steps overall.
报道了一种非对称途径来合成笼状四环吡咯烷生物碱——石斛碱。成功的合成策略具有一锅、连续钯催化烯炔环异构化和铑催化二烯辅助吡咯烷形成的特点，通过烯丙基 CH 活化。开发的过渡金属催化级联过程允许快速进入石斛碱核心结构，并避免处理不稳定的中间体。在精心定义的反应条件下进行分子内 aldol 缩合，同时进行脱甲氧基化，然后进行还原胺甲基化，仅通过 10 步总合成即可得到晚期中间体（以前通过几种石斛碱合成方法鉴定）。
