title: Effect of alcohol chain length on the enzymatic resolution of racemic mandelic acid and kinetic study.
abstract: Asymmetric esterification of racemic mandelic acid (MA) was conducted in 1,2-dichloroethane using lipase Novozym 435 as catalyst. Different alcohols were screened for esterification to achieve high conversion and enantioselectivity. The results show that ethanol is the best alcohol substrate among tested alcohols, and long-chain alcohols show lower enantioselectivities. The effect of substrate concentrations on esterification with ethanol was studied, and the result indicates an alcohol inhibition. To examine the mechanism of the alcohol chain length effect, the ping-pong bi-bi mechanism with competitive alcohol inhibition was applied to build a model. By comparing the kinetic parameters of methanol, ethanol, butanol, heptanol, and octanol, it was found that both the Michaelis constant and the inhibition constant of alcohol increase with the increase in alcohol chain length, indicating that the balance between nucleophilicity and the inhibition effect is the possible reason for the highest conversion and enantioselectivity as shown by ethanol.
authors.affiliation: College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, People's Republic of China; College of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang, Hunan, People's Republic of China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Pan
authors.forename: Ke-Wen
authors.initials: KW
authors.lastname: Tang
authors.forename: Chang-Qing
authors.initials: CQ
authors.lastname: He
authors.forename: Wei
authors.initials: W
authors.lastname: Yi
authors.forename: Wei
authors.initials: W
authors.lastname: Zhu
authors.forename: You-Nian
authors.initials: YN
authors.lastname: Liu
mesh_terms: D000438:Alcohols / Q000737:chemistry* / Q000378:metabolism*; D055162:Biocatalysis; D004800:Enzymes, Immobilized; D005656:Fungal Proteins; D007700:Kinetics; D008049:Lipase / Q000378:metabolism*; D008333:Mandelic Acids / Q000737:chemistry* / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D000438:Alcohols; D004800:Enzymes, Immobilized; D005656:Fungal Proteins; D008333:Mandelic Acids; C093667:Novozyme 435; D008049:Lipase; C037938:mandelic acid
keywords: (R,S)-mandelic acid; Novozym 435; asymmetric esterification; chain length; kinetic