The Asymmetric Synthesis of Fused Cyclopentenone Ring Systems: A formal asymmetric total synthesis of (?)-isocomene
作者:Albert I. Meyers、Stefan Bienz、Hyok-Boong Kwon、Richard H. Wallace
DOI:10.1002/hlca.19960790412
日期:1996.6.26
10 (R″ = H) via its enolate gives stereospecifically α-quaternary products 10 (R″ = alkyl). Degradation of the latter with MeLi or Red-Al® followed by mild acid hydrolysis and aldol cyclization produces the bicyclic ketones 14 and 15 as 1:1 mixtures, readily separated and isolated in > 99% ee. This sequence produced a known non-racemic intermediate 69 for the synthesis of (−)-isocomene.
光学活性的三环恶唑烷内酰胺10已经使用两种不同的途径制备(方案1)。它们可以通过双环的内酰胺的酸介导的分子内环化作用可以得到13经由其acyliminium中间体生产所附的五元,六元,七元三环系统。可替代地,10可通过手性氨基醇环化缩合与环戊烷-1,2-二羧酸制备12,得到被还原或烷基化的氨基醇与环化的非对映体混合物的酰亚胺10。的烷基化10(R“= H)通过其烯醇化物给出立体定向的α-季产物10(R ''=烷基)。后者用MeLi或Red- Al®降解,然后进行温和的酸水解和羟醛环化,生成双环酮14和15,为1:1混合物,易于分离并分离出> 99%ee。该序列产生了已知的用于合成(-)-异丁烯的非外消旋中间体69。