Asymmetric Synthesis of 2-Alkyl-Substituted 2,5-Dihydropyrroles from Optically Active Aza-Baylis−Hillman Adducts. Formal Synthesis of (−)-Trachelanthamidine.
作者:Shingo Ishikawa、Fumiaki Noguchi、Akio Kamimura
DOI:10.1021/jo100315j
日期:2010.6.4
the corresponding 2,3-disubstituted pyrrolidine in good yield. The stereoselectivity of the hydrogenation was sensitive to the presence or absence of the protective group in the C2-side chain. The TBS-protected 2,5-dihydropyrrole gave a 1:1 mixture of the cis/trans isomers, while free alcohol afforded the trans-2,3-disubstituted pyrrolidine in a selectivity of 6:1. The formal synthesis of (−)-trachelanthamidine
通过不对称的氮杂-Baylis-Hillman等效反应和随后的闭环易位反应,制备了一系列旋光的2-烷基取代的2,5-二氢吡咯。光学活性的氮杂-Baylis-Hillman加合物经历了平稳的两步转化为N-烯丙基-β-氨基-α-亚甲基酯的收率很高,几乎可以通过Grubbs催化剂催化的RCM反应定量地获得手性2,5-二氢吡咯,这是氮杂杂环合成的潜在前体。进行转化而不会损失起始原料的光学纯度。检验了该方法在(-)-trachelanthamidine中的合成应用。2,5-二氢吡咯的氢化顺利进行,以良好的产率得到相应的2,3-二取代的吡咯烷。氢化的立体选择性对C 2侧链中是否存在保护基敏感。TBS保护的2,5-二氢吡咯得到顺式/反式异构体的1:1混合物,而游离醇提供了反式-2,3-二取代的吡咯烷的选择性为6:1。(-)-trachelanthamidine的正式合成是从手性亚磺酰亚胺中分11步完成的