The irreversible transesterification of racemic 2-methyl-1,3-propanediol derivatives, the monoethers, 3a, 3b, 5a, and the monobenzoate 5b, with vinyl acetate catalyzed by Pseudomonasfluorescenslipase in chloroform affords enantiomerically pure chiral synthons.
Highlyefficient, direct, and enantioselectivesynthesis of useful chiral building blocks with excellent ee was performed by the catalytic asymmetric acylation of meso-1,3-propanediols. A structurally most simple meso-1,3-propanediol, 2-methyl-1,3-propanediol, was asymmetrized in 96% ee catalyzed by 0.5 mol% of chiral 1,2-diamine.
通过内消旋 1,3-丙二醇的催化不对称酰化,高效、直接和对映选择性合成具有优异 ee 的有用手性结构单元。结构上最简单的内消旋-1,3-丙二醇,即 2-甲基-1,3-丙二醇,在 0.5 mol% 的手性 1,2-二胺催化下,其 ee 不对称化率为 96%。
Desymmetrization of Meso 1,3- and 1,4-Diols with a Dinuclear Zinc Asymmetric Catalyst
作者:Barry M. Trost、Takashi Mino
DOI:10.1021/ja029708z
日期:2003.3.1
A dinuclear asymmetric zinc catalyst generated by mixing a 2:1 ratio of diethylzinc and 2,6-bis[5-2-diarylhydroxy methyl-1-pyrrolidinyl]-4-methylphenol has been contrasted with enzymes for the desymmetrization of some meso diols. The best ligand has a p-biphenylyl group as the aromatic substituent defining the chiral space. A series of 2-substituted propanediols were examined. The best acyl transfer agent proved to be vinyl benzoate. Diacylation normally did not occur. The phenyl substituted substrate gave 91-95% ee which compares favorably with the best ee of 92% reported for an enzymatic desymmetrization. The methyl substituted substrate gave significantly better results with the dinuclear zinc catalyst (89% yield, 82% ee) as compared to the best enzymatic esterification (70% yield, 60% ee). One case of a 1,4-diol, cis-1,2-bis(hydroxymethyl) cyclohexane, also gave much better results with the dinuclear zinc catalysts (93% yield, 91% ee) as compared to the reported enzymatic process (44% yield, 7% ee). A model to rationalize the results is presented.
Asymmetrization of 2-methylpropane-1,3-diol by Mucor miehei lipase-catalyzed benzoylation in organic solvent
Asymmetrization of prochiral 2-methylpropane-1,3-diol by Mucor miehei lipase (MML)-catalyzed acylation with vinyl benzoate affords the corresponding (S)-monobenzoate (65% ee), which can be obtained enantiomerically pure in 40% yield from a sequential benzoylation procedure at 58% conversion of the diol to the corresponding dibenzoate. (C) 2004 Elsevier Ltd. All rights reserved.