Application of ionic liquids in enzymic resolution by hydrolysis of cycloalkyl acetates

A comparative study was performed in the enzymic resolution of the isomers of 2-(4-methoxybenzyl)cyclohexyl acetates 1 and 2. The investigation consisted in application of three commercially available lipases (Novozyme 435, Lipozyme IM and non-immobilized powdered lipase from Candida antarctica), two ionic liquids (1-butyl-4-methylpyridinium chloride and 1,3-dimethylimidazolinium methyl sulfate), three modifications of the reaction conditions and two respective isomers of the racemic substrate (1 and 2), and resulted in our finding the appropriate conditions to get both of the products, stereoisomers of 2-(4-methoxybenzyl)cyclohexanol (3; 1S,2S) or (5; 1S,2R), and (in some cases) also the stereoisomers of the deracemized substrate (4; 1R,2R) or (6; 1R,2S) with high or acceptable enantiomeric purity.

Enzyme resolution of the isomers of 2-(4-methoxybenzyl)cyclohexyl acetate was studied employing three commercially available lipases, two ionic liquids, three modifications of the reaction conditions and two respective isomers of the racemic substrate, 2-(4-methoxybenzyl)cyclohexyl acetate.Figure optionsDownload as PowerPoint slide

(1S,2S)-2-(4-Methoxybenzyl)cyclohexanolC14H20O2Ee >99%[α]D20=+34.4 (c 0.116, CHCl3)Source of chirality: enzymic resolution by lipase-mediated hydrolysisAbsolute configuration: (1S,2S)

(1S,2R)-2-(4-Methoxybenzyl)cyclohexanolC14H20O2Ee >99%[α]D20=-21.3 (c 0.083, CHCl3)Source of chirality: enzymic resolution by lipase-mediated hydrolysisAbsolute configuration: (1S,2R)