(<i>3R</i>)-Chiral Control of 3-Alkyl-3-hydroxy-β-lactams via Addition Reaction of Imines to Enolates of 1,3-Dioxolan-4-ones
作者:Gaetano Barbaro、Arturo Battaglia、Andrea Guerrini、Carlo Bertucci
DOI:10.1021/jo9822481
日期:1999.6.1
self-regeneration of stereocenters and has been applied to addition reactions among a selected number of imines and (2S)-chiral enolates of 1,3-dioxolan-4-ones. These reagents are easily available from the acetalization of (S)-alpha-hydroxy acids (lactic, mandelic, isovaleric, malic) and pivalaldehyde or pinacolone. In several cases, the addition of the enolate to the imine, the cyclization, and the removal of
描述了一种以通用且可预测的方式手性构建(3R)-3-烷基-3-羟基-β-内酰胺的方法。该方案遵循Seebach立体中心自我再生的合成原理,并已应用于选定数量的1,3-二氧杂戊环-4-酮亚胺和(2S)-手性烯酸酯之间的加成反应。这些试剂很容易从(S)-α-羟基酸(乳酸,扁桃,异戊酸,苹果酸)和新戊醛或频哪酮的缩醛化中获得。在某些情况下,将烯酸酯添加到亚胺中,环化并去除辅助中心是一步一步完成的,提供了相应的β-内酰胺,如(3R,4S)-Z和(3R,4R )-E对映体过量的非对映体混合物。四个带有2-呋喃基(4e)的N-未取代的(3R,4S)-3-羟基-3-甲基-β-内酰胺,获得C4处的苯基乙烯基(4h),甲氧基羰基(4i)和2-噻吩基(4l)取代基作为主要的非对映异构体,并通过结晶纯化。这些取代基同时存在于C3和C4处,使这些β-内酰胺成为合成新紫杉烷类的有用中间体,新的紫杉类化合物在异丝氨酸部分具有有趣的结构修饰。