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

Insect pest control agents: Novel chiral butanoate esters (juvenogens)

During the investigation of ester derivatives (juvenogens, biochemically activated insect hormonogenic compounds) of biologically active alcohols with potential application in insect pest control, a need for availability of all existing stereoisomers of ethyl N-{2-[4-(2-butanoyloxycyclohexyl)methyl]phenoxy}ethyl carbamate occurred. They were synthesized from their chiral precursors, the corresponding stereoisomers of 2-(4-methoxybenzyl)cyclohexyl butanoate, by removing their protecting group (methyl), and by subsequent condensation of the aromatic hydroxyl moiety with ethyl N-(2-bromoethyl) carbamate. The requested enantiomers of 2-(4-methoxybenzyl)cyclohexyl butanoate were obtained by a Candida antarctica lipase-mediated transesterification and chiral resolution of the respective racemic cis- and trans-isomers of 2-(4-methoxybenzyl)cyclohexanol either directly or after a subsequent chemical esterification of the chiral precursor. In this synthesis, two convenient butanoic acid activating esters, vinyl butanoate and 2,2,2-trifluoroethyl butanoate, were employed, and the chiral precursors in the synthesis of the target molecules were obtained in 41\u201348% yields (i.e., 82\u201396% conversion), and with enantiomeric purity ee = 96\u201398%, respectively. The enantiomeric purity of the products was determined by chiral HPLC analysis, and their absolute configuration was assigned on the basis of analyzing the 1H and 19F NMR spectra of their diastereoisomeric Mosher acid (3,3,3-trifluoromethyl-2-methoxy-2-phenylpropanoic acid) esters

Lipase activity enhancement by SC-CO2 treatment

The activity of lipases from porcine pancreas, Candida antartica recombinant from Aspergillus oryzae, Candida cylindracea (immobilized), Penicilium roqueforti, Aspergillus niger, Rhizopus arrhizus, Mucor miehei (two types of immobilization), and Pseudomonas cepacia (two types of immobilization) was studied after using them as biocatalysts of blackcurrant oil hydrolysis under SC-CO2 conditions. The reaction was performed at 40°C and 15 MPa in a continuous-flow reactor. Increased relative activity of all used lipases after the hydrolytic reaction was observed. The most remarkable increase in the activity was noted for the lipase from Rhizopus arrhizus which was increased by more than 50 times. The highest activity was shown by Lipozyme®, lipase from Mucor miehei, immobilized on macroporous resin. Both treated and untreated Lipozyme® were used as biocatalysts in hydrolytic resolution of the racemic cis- or frani-isomers of 2-(4-methoxybenzyl) cyclIohexyl acetates. Satisfactory reaction yields (40 %) and excellent enantiomeric purity of the products (E = 472) were obtained when hydrolysis of the frans-isomer of 2-(4-methoxybenzyl)cyclohexyl acetate was catalyzed by Lipozyme® treated with SC-CO2. © 2008 Verlag der Zeitschrift für Naturforschung, Tübingen