An Efficient and Enantioselective Approach to the Azaspirocyclic Core of Alkaloids: Formal Synthesis of Halichlorine and Pinnaic Acid
作者:Hong-Lu Zhang、Gang Zhao、Yu Ding、Bin Wu
DOI:10.1021/jo047882v
日期:2005.6.1
A novel, highly stereoselective synthesis of an azaspirocyclic core, which contains four stereogenic carbons consistent with structures of natural halichlorine and pinnaic acid, is presented. Lipase PS-catalyzed selective acylation, asymmetric methylation on the α-methylene of the bicyclic lactone, and an asymmetric Michael addition of the tertiary nitro cyclopentane were concisely used to conquer
提出了一种新颖的,高度立体选择性的氮杂螺环核心合成,该核心含有四个与自然盐酸盐和松果酸结构一致的立体碳。脂肪酶PS催化的选择性酰化,双环内酯的α-亚甲基上的不对称甲基化以及叔硝基环戊烷的不对称Michael加成反应,可以解决成功构建具有完全立体控制的C9季碳中心的难题。螺哌啶环的形成是通过还原δ-硝基酮,分子内缩合,然后用NaBH 4高度立体选择性地还原环硝酮。这个螺环核心是Danishefsky合成频烷酸和盐酸的关键中间体。