Improved Preparation and Use of Room-Temperature Ionic Liquids in Lipase-Catalyzed Enantio- and Regioselective Acylations

Abstract

Polar organic solvents such as methanol or N-methylformamide inactivate lipases. Although ionic liquids such as 3-alkyl-1-methylimidazolium tetrafluoroborates have polarities similar to these polar organic solvents, they do not inactivate lipases. To get reliable lipase-catalyzed reactions in ionic liquids, we modified their preparation by adding a wash with aqueous sodium carbonate. Lipase-catalyzed reactions that previously did not occur in untreated ionic liquids now occur at rates comparable to those in nonpolar organic solvents such as toluene. Acetylation of 1-phenylethanol catalyzed by lipase from Pseudomonas cepacia (PCL) was as fast and as enantioselective in ionic liquids as in toluene. Ionic liquids permit reactions in a more polar solvent than previously possible. Acetylation of glucose catalyzed by lipase B from Candida antarctica (CAL-B) was more regioselective in ionic liquids because glucose is up to one hundred times more soluble in ionic liquids. Acetylation of insoluble glucose in organic solvents yielded the more soluble 6-O-acetyl glucose, which underwent further acetylation to give 3,6-O-diacetyl glucose (2-3:1 mixture). However, acetylation of glucose in ionic liquids yielded only 6-O-acetyl glucose (>13:1 and up to >50:1).

Ionic liquids in biotechnology: applications and perspectives for biotransformations

“…The regioselective acylation of β-D-glucose with CALB (Novozym SP435) in two different organic solvents (acetone, THF) and eight IL was carried out (Park and Kazlauskas 2001) A number of investigations shows that IL as additive or solubiliser for aqueous systems can influence activity and selectivity and allows the conversion of otherwise insoluble substrates.…”

Enzymatic Hydrolytic Resolution of Racemic Ibuprofen Ethyl Ester Using an Ionic Liquid as Cosolvent

“…The use of enzymes, especially lipases, in ionic liquids, has demonstrated many advantages, such as high conversion rates, good enantioselectivity, better recoverability and recyclability. For example, the stability of lipases such as CaLB [13][14][15][16] and Pseudomonas cepacia lipase (PcL) [15,17] are catalytically active in imidazolium and pyridinium ILs containing BF 4´, PF 6´a nd Tf 2 N´ [14]. [OmPy][BF 4 ] provide high enantioselectivity to hesperidinase when used as co-solvent in the enzymatic conversion of rutin to isoquercitrin.…”

Using Ionic Liquids for the Separation of Carbohydrates

“…It was then reported that the dicyanamide is an attractive anion to dissolve carbohydrates, due to its hydrogen bond acceptor properties [9]- [12]. N, N-methylmethoxyalkylimidazolium was reported to have a sugar-philic cation, rather than anion [10]- [13].…”