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Enantiopure intermediates are preferred for drug synthesis in pharmaceutical industry. Lipases are widely used for chiral resolution of optically active compounds based on kinetic resolution. In the kinetic resolution, two enantiomers react with different rates in presence of a chiral catalyst or reagent, resulting in obtaining one enantiomer of great excess compared to other. The enantiomeric ratio (E) is closely related to the free energy difference (ΔΔG) of the activated state of substrate enantiomers. Molecular dynamic (MD) simulations with umbrella sampling technique can be used for estimation of activation free energy change of enantiomers. In this work, lipase-catalyzed transesterification of racemic alcohols with single and double hydroxyl groups have been studied. The umbrella sampling studies have been carried out for Candida rugosa lipase and Burkholderia cepacia lipase in n-hexane. The distance between serine residue in the catalytic triad and the ligand has been considered as a reaction coordinate and various conformations have been selected for MD simulation. The E value has been estimated based on free energy change from umbrella sampling. The estimated E values are in good agreement with experimental data. The work highlights changes in lipase conformation in n-hexane, ligand-protein interaction as well as free energy curve as a function of the reaction coordinate., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Kinetic resolution of rac-1,2-diols using the biocatalyst Burkholderia cepacia lipase (BCL) immobilized on a biodegradable binary blend support of hydroxypropyl methyl cellulose(HPMC)/polyvinyl alcohol (PVA) has been investigated. The immobilization technique improved enzyme activity significantly and it has excellent recyclability with good yield and enantiomeric excess values up to the studied range of nine cycles. At optimum reaction conditions, conversion of 45-50% with excellent enantiomeric excess (up to 99% ee) were obtained. It was observed that BCL shows enantio-preference to R form of primary hydroxyl group for acylation, whereas S form is preferred for diacetate formation. The resultant products were characterized with the help of different analytical techniques such as 1 H and 13 C NMR, chiral HPLC, IR and GC-MS. In order to understand the effect of solvent as well as various derivatives of substrates, combined molecular dynamics and docking simulations were carried out. Explanation related to experimentally observed enantio-selectivities have been provided based on transition state structures of acylated complexes., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The present work deals with the kinetic modeling and docking study for the furfuryl acetate synthesis using immobilized Burkholderia cepacia (BCL) lipase. Initially various lipases were immobilized on hydroxypropyl methyl cellulose (HPMC) and poly vinyl alcohol (PVA) base hybrid polymer matrix. After screening of various immobilized biocatalysts, HPMC:PVA:BCL was found to be a robust biocatalyst. Various reaction conditions were optimized using response surface methodology (RSM) based on a four-factor-three-level Box-Behnken design. The optimal conditions were obtained at molar ratio of 1:2 of furfuryl alcohol to acyl donor, temperature 50°C with catalyst loading of 30mg in 3mL of non-aqueous media toluene. Under these conditions 99.98% yield was obtained in 3h. The Arrhenius plot showed that the activation energy for furfuryl acetate synthesis was 10.68kcal/mol. The kinetics of reaction was studied close to optimized conditions which obey order bi-bi model. Molecular docking study was carried out to understand the active site of BCL which is responsible for the reaction. It was observed that the reaction proceeds via acylation of the active serine of BCL and demonstrating strong hydrogen bond between the substrate and histidine site. The catalyst recyclability study was carried up to five cycles., (Copyright © 2015 Elsevier Inc. All rights reserved.)