Desymmetrisation of 4,4-disubstituted cyclohexanones by enzyme-catalysed resolution of their enol acetates
作者:Graham Allan、Andrew J. Carnell、Maria Luisa Escudero Hernandez、Alan Pettman
DOI:10.1039/b005466f
日期:——
Enol acetates 3–10 derived from prochiral 4,4-disubstituted cyclohexanones can be resolved with Pseudomonas fluorescens lipase to give enantiomerically pure (>99% ee) enol esters by transesterification with n-BuOH. The product ketones are prochiral and can easily be recycled giving an overall desymmetrisation of the ketone. Highest selectivity was obtained for substrates containing a 4-cyano and 4-aryl or a 4-benzyloxy substituent. The methodology was compared to asymmetric deprotonation–enolate trapping using the chiral base (S,S)-bis(α-methylbenzyl)amide which gave low (54–64%) ee’s for this class of ketones.
来自对称的4,4-二取代环己酮的醇乙酸酯3-10可以通过荧光假单胞菌脂肪酶进行分离,以转酯化反应与正丁醇生成对映体纯度>99% ee的醇酯。生成的酮是对称的,可以很容易地循环利用,从而实现酮的整体去对称化。对于含有4-氰基和4-芳基或4-苄氧基取代基的底物,获得了最高的选择性。该方法与使用手性碱(S,S)-双(α-甲基苯甲酰)胺的非对称去质子化-烯醇捕获进行了比较,该方法在这一类酮中获得了较低的对映体纯度(54-64% ee)。