Stereoselectivity in N-Iminium Ion Cyclization: Development of an Efficient Synthesis of (±)-Cephalotaxine.
Stereoselectivity in N-Iminium Ion Cyclization: Development of an Efficient Synthesis of (±)-Cephalotaxine.
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DOI：
10.1021/acs.orglett.5b02106
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发表时间：
2015-09
期刊：
影响因子：
5.2
通讯作者：
Hao Liu;Jing Yu;Xinyu Li;Rui Yan;Jianhua Xiao;R. Hong
中科院分区：
文献类型：
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作者：
Hao Liu;Jing Yu;Xinyu Li;Rui Yan;Jianhua Xiao;R. Hong
采用N-亚胺离子与烯丙基硅烷的立体选择性环化反应，构建了邻位的四、三碳中心，用于(±)-三尖杉碱的简单合成。目前的策略以TiCl4促进的环化和闭环歧化为特征来提供螺环系统。用Z-或E-烯丙基硅烷的立体电子效应对N-酰亚胺离子环化的立体化学结果进行了合理化。环化反应中产生的两个非对映异构体合并成(±)-三尖杉碱的正式合成。
A stereoselective N-iminium ion cyclization with allylsilane to construct vicinal quaternary-tertiary carbon centers was developed for the concise synthesis of (±)-cephalotaxine. The current strategy features a TiCl4-promoted cyclization and ring-closure metathesis to furnish the spiro-ring system. The stereochemical outcome in the N-acyliminium ion cyclization was rationalized by the stereoelectronic effect of the Z- or E-allylsilane. Two diastereomers arising from the cyclization were merged into the formal synthesis of (±)-cephalotaxine.