Stereoelectronic Effects Dictate Mechanistic Dichotomy between Cu(II)-Catalyzed and Enzyme-Catalyzed Reactions of Malonic Acid Half Thioesters
作者:Kevin C. Fortner、Matthew D. Shair
DOI:10.1021/ja0673682
日期:2007.2.1
Previously we developed a Cu(II)-catalyzed, enantioselective aldol reaction between malonic acid half thioesters (MAHTs) and aldehydes based on the biosynthesis of polyketides and fatty acids in which MAHTs are decarboxylated enzymatically to afford ester enolates that condense with thioesters. We report evidence based on steric effects, kinetics, kinetic isotope effects, and crossover experiments in support
以前,我们基于聚酮化合物和脂肪酸的生物合成,在其中 MAHT 酶促脱羧以提供与硫酯缩合的酯烯醇化物,在丙二酸半硫酯 (MAHT) 和醛之间开发了 Cu(II) 催化的对映选择性羟醛反应。我们报告了基于空间效应、动力学、动力学同位素效应和交叉实验的证据,以支持 Cu(II) 催化的羟醛反应的不同机制,包括通过去质子化、添加到醛、脱羧和质子化 MAHT 的烯醇化β-羟基烯醇化物。我们还基于立体电子效应对 MAHT 的 Cu(II) 催化和酶催化反应之间的机械二分法进行了解释。