title: Stereoselectivity of the generation of 3-mercaptohexanal and 3-mercaptohexanol by lipase-catalyzed hydrolysis of 3-acetylthioesters.
abstract: The enantioselectivity of the generation of 3-mercaptohexanal and 3-mercaptohexanol, two potent sulfur-containing aroma compounds, by lipase-catalyzed hydrolysis of the corresponding 3-acetylthioesters was investigated. The stereochemical course of the kinetic resolutions was followed by capillary gas chromatography using modified cyclodextrins as chiral stationary phases. The enzyme preparations tested varied significantly in terms of activity and enantioselectivity (E). The highest E value (E = 36) was observed for the hydrolysis of 3-acetylthiohexanal catalyzed by lipase B from Candida antarctica resulting in (S)-configured thiol products. Immobilization of the enzyme (E = 85) and the use of tert-butyl alcohol as cosolvent (E = 49) improved the enantioselectivity. Modification of the acyl moiety of the substrate (3-benzoylthiohexanal) had no significant impact. The sulfur-containing compounds investigated possess attractive odor properties, and only one of the enantiomers exhibits the pleasant citrus type note.
authors.affiliation: Lehrstuhl für Allgemeine Lebensmitteltechnologie, Technische Universität München, Am Forum 2, D-85350 Freising-Weihenstephan, Germany.
authors.forename: Hidehiko
authors.initials: H
authors.lastname: Wakabayashi
authors.forename: Motoko
authors.initials: M
authors.lastname: Wakabayashi
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eisenreich
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Engel
mesh_terms: D000447:Aldehydes / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001230:Aspergillus / Q000201:enzymology; D002175:Candida / Q000201:enzymology; D004952:Esters / Q000378:metabolism*; D000441:Hexanols / Q000737:chemistry / Q000378:metabolism*; D006868:Hydrolysis; D008049:Lipase / Q000378:metabolism*; D008099:Liver / Q000201:enzymology; D009089:Mucor / Q000201:enzymology; D009812:Odorants; D010407:Penicillium / Q000201:enzymology; D012233:Rhizopus / Q000201:enzymology; D013237:Stereoisomerism; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000737:chemistry / Q000378:metabolism*; D013552:Swine
chemical_list: D000447:Aldehydes; D004952:Esters; D000441:Hexanols; D013438:Sulfhydryl Compounds; C477018:3-mercaptohexanal; D008049:Lipase; C477019:3-mercaptohexanol