Efficient kinetic resolution of (R,S)‐1‐trimethylsilylethanol via lipase‐mediated enantioselective acylation in ionic liquids

Abstract

Efficient enantioselective acylation of (R,S)-1-trimethylsilylethanol {(R,S)-1-TMSE} with vinyl acetate catalyzed by immobilized lipase from Candida antarctica B (i.e., Novozym 435) was successfully conducted in ionic liquids (ILs). A remarkable enhancement in the initial rate and the enantioselectivity of the acylation was observed by using ILs as the reaction media when compared to the organic solvents tested. Also, the activity, enantioselectivity, and thermostability of Novozym 435 increased with increasing hydrophobicity of ILs. Of the six ILs examined, the IL C4MIm.PF6 gave the fastest initial rate and the highest enantioselectivity, and was consequently chosen as the favorable medium for the reaction. The optimal molar ratio of vinyl acetate to (R,S)-1-TMSE, water activity, and reaction temperature range were 4:1, 0.75, and 40 -50 degrees C, respectively, under which the initial rate and the enantioselectivity (E value) were 27.6 mM/h and 149, respectively. After a reaction time of 6 h, the ee of the remaining (S)-1-TMSE reached 97.1% at the substrate conversion of 50.7%. Additionally, Novozym 435 was effectively recycled and reused in C4MIm.PF6 for five consecutive runs without substantial lose in activity and enantioselectivity. The preparative scale kinetic resolution of (R,S)-1-TMSE in C4MIm.PF6 is shown to be very promising and useful for the industrial production of enantiopure (S)-1-TMSE.

Influence of ionic liquids under controlled water activity and low halide content on lipase activity

“…In the direct esterification of geraniol with acetic acid using [Bmim][PF 6 ], optimal a w was 0.6 and enzyme activity was low for both high and low a w [20]. The analogous result was obtained in the acylation of 1-trimethylsilylethanol with vinyl acetate using [Bmim][PF 6 ] (optimal a w =0.75) [21]. Although the optimal a w can be changed by temperature, pressure, reactant concentrations, and direct water participation [22], these results showed severely different optimal a w of Novozym 435.…”

“…Similar results for the influence of anion structure on the lipasecatalyzed esterifications using anhydrous ILs have been reported [8,19,21,29]. However, several conflicting results were also reported for the acetylation of 1-phenylethanol using Candida antarctica lipase B or Pseudomonas cepacia lipase [2,6,30].…”

Surface display of active lipase in Pichia pastoris using Sed1 as an anchor protein

“…The extracellular lipase of Candida antarctica, lipase B (CALB), which is an efficient catalyst of hydrolysis, esterification and transesterification reactions, has been used in the alcoholysis of oils, for example in the production of biodiesel (Torres et al 2004;Modi et al 2006), the synthesis of short-chain flavor esters (Larios et al 2004;Han et al 2009), and for kinetic resolution (Fransson et al 2006;Lou and Zong 2006). However, the high cost of the enzyme is a limiting factor.…”

Compatibility of Ionic Liquids with Enzymes

“…In some reports, ionic liquids with long alkyl chain in cations may behave as surfactants in aqueous solution and have strong stabilizing impact on enzyme [56,57]. However, in some cases, the long alkyl chain might have negative effect on the activity and stability of enzyme due to the resulted higher viscosity [58]. In practice, the log P (logarithm of partition coefficient between octanol and water) scale can be used to quantify the hydrophobicity of ionic liquids, and in some reports this scale can be used to optimize enzyme activity and stability in ionic liquids [21,46,59,60].…”