title: Metal ions dramatically enhance the enantioselectivity for lipase-catalysed reactions in organic solvents.
abstract: We propose a simple and a powerful method to enhance the enantioselectivity for lipase-catalysed transformations in organic solvents by an addition of metal ion-containing water to the reaction mixture. In this paper, various metal ions such as LiCl or MgCl2 are tested to improve the enantioselectivity for the model reactions. The enantioselectivities obtained are dramatically enhanced, the E values of which are about 100-fold as compared with the ordinary conditions without a metal ion, for example, E = 200 by addition of LiCl. Furthermore, lowering the reaction temperature led to an almost perfect enantioselectivity of lipase in the presence of a metal ion, for example, E = 1,300 by addition of LiCl. Also, a mechanism for the drastic enhancement by metal ions is discussed briefly on the basis of the EPR spectroscopic study and the initial rate for each enantiomer of the substrate.
authors.affiliation: Graduate School of Science and Technology, Kobe University, Nada, Kobe 657-8501, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Okamoto
authors.forename: Ebara
authors.initials: E
authors.lastname: Yasuhito
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Ueji
mesh_terms: D002175:Candida / Q000201:enzymology; D004578:Electron Spin Resonance Spectroscopy; D005656:Fungal Proteins / Q000378:metabolism; D007700:Kinetics; D008049:Lipase / Q000378:metabolism*; D018021:Lithium Chloride / Q000494:pharmacology; D008670:Metals / Q000494:pharmacology*; D009930:Organic Chemicals; D012997:Solvents; D013237:Stereoisomerism
chemical_list: D005656:Fungal Proteins; D008670:Metals; D009930:Organic Chemicals; D012997:Solvents; D008049:Lipase; D018021:Lithium Chloride