Chemoenzymatic Synthesis of α-Hydroxy-β-methyl-γ-hydroxy Esters: Role of the Keto−Enol Equilibrium To Control the Stereoselective Hydrogenation in a Key Step
作者:Cíntia D. F. Milagre、Humberto M. S. Milagre、Paulo J. S. Moran、J. Augusto R. Rodrigues
DOI:10.1021/jo902227f
日期:2010.3.5
α-Hydroxy-β-methyl-γ-hydroxy esters not only are found in many natural products and potent drugs but also are useful intermediates in organic synthesis due to their highly functionalized skeleton that can be further manipulated and applied in the synthesis of many compounds with remarkable biological activities. This work was based on a chemoenzymatic approach to obtain these molecules with three contiguous
α-羟基-β-甲基-γ-羟基酯不仅存在于许多天然产物和强效药物中,而且由于其高度官能化的骨架可以进一步操纵并应用于许多化合物的合成中,因此它们是有机合成中有用的中间体具有出色的生物活性。这项工作基于化学酶法,以高度对映和非对映选择性的方式获得具有三个连续的立体中心的这些分子。提出了两种不同的线性途径,其中两种途径中的关键步骤包括:初始立体控制的酮酯生物还原,然后是不饱和羰基生物还原或用Pd-C还原。合成中的其他关键反应包括用于链同源化的Wasserman方案和曼尼希(Mannich)型烯化反应,并维持序列中所有中间体的对映体过量。而路线A仅给骨架3个R,4 R,5 S构型(7个步骤后ee为99%,总产率为11.5%),路线B给出了具有3 R,4 R,5 S和3 R,4 S,5 R构型的骨架(dr 1: 12、98%ee和5步后全球总产量的20%)。