Ionic Liquid Medaited Activation of Enzymatic Reactions

我们发现，当一种新的离子液体，即咪唑聚氧乙烯（10）十六烷基硫酸盐以3至10摩尔%相对于底物的洋葱伯克霍尔德菌脂肪酶催化的酯交换反应的仲醇使用乙酸乙烯酯在二异丙醚或己烷溶剂系统中，获得增强的对映体选择性。此外，我们发现，一个显着的加速也得到了当脂肪酶用这种离子液体涂覆，同时仍然保持良好的对映选择性。已经报道了仅有限的实现脂肪酶催化反应的加速和增强的对映体选择性的手段的实例：PEG涂层可以加速反应，但没有引起显著增强的对映体选择性;此外，使用甲苯作为溶剂引起对某些底物的增强的对映体选择性，但没有引起反应的显著活化。我们在制备IL 1包被的脂肪酶PS时，对于1.0 g脂肪酶仅使用28 mg IL;该量实际上是微量的。我们 ...更多信息 假设这可能是由于IL的特殊性质，因为它由咪唑鎓阳离子和阴离子PEG硫酸盐组成，并且这两个部分可能协同促进脂肪酶的活化。这是本发明的使用离子液体的脂肪酶活化方法的主要概念。离子液体现在被认为是脂肪酶催化反应中使用的溶剂，但是，仍然存在着在离子液体中的反应速率比在常规有机溶剂中的反应速率慢的严重缺点。为了克服这个问题，已经尝试开发适合于脂肪酶催化的反应的鳞离子液体;已经制备了几种类型的鳞盐，并且评估了它们用作脂肪酶催化的反应的溶剂的能力。以2-甲氧基乙基（三正丁基）磷鎓双（三氟甲磺酰基）酰亚胺（[MEB_ P][NTf_2]）为溶剂，脂肪酶PS催化仲醇的酯交换反应速度非常快<u3>，反应速率上级优于二异丙醚。少

We discovered that enhanced enantioselectivity was obtained when a novel ionic liquid, i.e. imidazolium polyoxyethylene(10) cetyl sulfate was added at 3 to 10 mol% vs. substrate in the Burkholderia cepacia lipase-catalyzed transesterification of sec-alcohols using vinyl acetate in diisopropyl ether or a hexane solvent system. Further, we found that a remarkable acceleration was also obtained when the lipase was coated with this ionic liquid while still maintaining excellent enantioselectivity. There have been reported only limited examples of means to achieve both acceleration and enhanced enantioselectivity of lipase-catalyzed reaction: PEG coating could accelerate the reaction but caused no significant enhanced enantioselectivity; also, using toluene as solvent caused enhanced enantioselectivity for some substrates but caused no significant activation of the reaction. We used only 28 mg of IL for 1.0 g of lipase in preparing our IL1-coated-lipase PS; the amount was really a trace. We … More assume this might be due to the special nature of IL because it consists of imidazolium cation with anionic PEG sulfate and both parts might cooperatively contribute to the activation of the lipase. This is the main concept of our lipase activation method using an ionic liquid.Ionic liquids are now recognized as solvents for use in lipase-catalyzed reactions, however, there still remains a serious drawback in that the rate of reaction in an ionic liquid is slower than that in a conventional organic solvent. To overcome this problem, attempts have been made to evolve phosphonium ionic liquids appropriate for lipase-catalyzed reaction; several types of phosphonium salts have been prepared and their capability evaluated for use as solvent for the lipase-catalyzed reaction. Very rapid lipase PS-catalyzed transesterification of secondary alcohols was obtained when 2-methoxyethyl(tri-n-butyl)phosphonium bis(trifluoromethanesulfonyl)imide ([MEB_<u3>P][NTf_2]) was used as solvent, affording the first example of a reaction rate superior to that in diisopropyl ether. Less