Several types of imidazolium salt ionic liquids were prepared derived from poly(oxyethylene)alkyl sulfate and used as an additive or coating material for lipase-catalyzed transesterification in an organic solvent. A remarkably increased enantioselectivity was obtained when the salt was added at 3-10 mol % versus substrate in the Burkholderia cepacia lipase (lipase PS-C)-catalyzed transesterification of 1-phenylethanol by using vinyl acetate in diisopropyl ether or a hexane solvent system. In particular, a remarkable acceleration was accomplished by the ionic liquid coating with lipase PS in an iPr(2)O solvent system while maintaining excellent enantioselectivity; it reached approximately 500- to 1000-fold acceleration for some substrates with excellent enantioselectivity. A similar acceleration was also observed for IL 1-coated Candida rugosa lipase. MALDI-TOF mass spectrometry experiments of the ionic-liquid-coated lipase PS suggest that ionic liquid binds with lipase protein.

Stimulating the hunger of enzymes: The design of an ionic liquid that has the ability to dissolve cellulose has been attempted from the viewpoint of a cellulase. N,N‐diethyl‐N‐(2‐methoxyethyl)‐N‐methylammonium alanine ([N221ME][Ala]) is a good solvent for cellulose. Dissolution in [N221ME][Ala] converts the crystalline structure of cellulose from Type I to II, which is known to be a form easily digested by cellulases.

A rational design of phosphonium ionic liquid for ionic liquid coated-lipase (IL1-PS)-catalyzed reaction has been investigated, and very rapid transesterification of secondary alcohols accomplished when IL1-PS was used as catalyst in 2-methoxyethoxymethyl(tri-n-butyl)phosphonium bis(trifluoromethanesulfonyl)amide ([P 444MEM ][NTf 2 ]) as solvent while perfect enantioselectivity was maintaining. Increased K cat value was suggested to be the most important factor in IL1-PS working the best in [P 444MEM ][NTf 2 ] solvent.

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The synergetic effect of amino acids and an ionic liquid, 1-butyl-2,3-dimethylimidazolium ¡-cetylpolyoxyethylene(10) ether sulfate (IL1), as coating materials on lipase was discovered: coating on lipase PS using a certain amino acid with IL1 was found to be very effective for accelerating the lipase-catalyzed transesterification of secondary alcohols while maintaining perfect enantioselectivity.Lipases are among the most widely used enzymes applicable for various substrates; however, the reaction rate and enantioselectivity depend significantly on both the substrates and reaction media: the reaction rates are generally dependent on the reaction media, and very slow or poorly enantioselective reactions are sometimes obtained. 1We have been investigating enzymatic reactions in the ionic liquid (IL) solvent system and have established that various types of ILs are applicable as solvents for biochemical reactions. 24 We further developed a powerful method for the activation of lipase protein through coating with an ionic liquid: Burkholderia cepacia lipase coated with the ionic liquid, 1-butyl-2,3-dimethylimidazolium ¡-cetylpolyoxyethylene(10) ether sulfate (IL1), 5,6 (IL1-PS), displayed excellent reactivity for many substrates in conventional organic solvents 5 and ionic liquids. 7Luo and co-workers reported the preparation of chiral imidazolium salts derived from proline. 8 Inspired by their work, we prepared two types of chiral pyrrolidine-substituted imidazolium ¡-cetylpolyoxyethylene(10) ether sulfate, and found that (R)-3-butyl-2-methyl-1-(pyrrolidin-2-ylmethyl)-1H-imidazol-3-ium ¡-cetylpolyoxyethylene(10) ether sulfate (D-ProMe) derived from D-proline worked as an excellent activating agent for lipase PS (Figure 1). 9 An extraordinary acceleration was accomplished with perfect enantioselectivity for the D-ProMe-PS-catalyzed reaction, and a reaction 58 times faster (vs. lipase PS) was recorded.9 However, more simple coating materials need to be developed for the activation of lipase. We herein report the synergetic activation of amino acids and IL1 as a coating material for lipase.Amino acids have been used as stabilizers of enzymes during the purification process. For example, commercial lipase PS contains ca. 20 wt % glycine as an essential stabilizer during the preparation of the lipase protein through the lyophilization process. 5b We investigated the role of glycine and established that it worked only as a stabilizer of the enzyme and had no influence on the reactivity of lipase PS. 5b Since it was anticipated that a chiral amino acid may modify the enantioselectivity of an enzymatic reaction, we next prepared amino acidcoated lipase PS and investigated its properties in the transesterification of («)-1-phenylethanol (1a) as a model substrate in the presence of vinyl acetate as an acyl donor in the i-Pr 2 O solvent system (Figure 2). 10 As shown in Figure 2, the coating of lipase PS with amino acids neither accelerated the reaction nor modified its enantioselectivity, although coating lipase with L-asp...