Antioxidants eliminate stereomutation and thioether formation during lipase-catalyzed thioesterification and transthioesterification for the preparation of uniform cis- and trans-unsaturated thioesters.
The lipase-catalyzed preparation of acyl thioesters from unsaturated fatty acids and alkanethiols is accompanied by the formation of geometrical isomers via stereomutation and of thioether derivatives via addition at the olefinic bond, both induced by thiyl radicals. Therefore, a method was developed in order to inhibit radical generation by the addition of antioxidants and thus prevent the formation of geometrical isomers and thioether derivatives during the lipase-catalyzed preparation of unsaturated acyl thioesters. In the presence of antioxidants such as 2,6-di-t-butyl-4-methylphenol (BHT) and octyl gallate thioesterification of oleic and elaidic acids with 1-tetradecanethiol as well as transthioesterification of methyl linoleate with 1-tetradecanethiol led to the corresponding geometrically uniform thioesters without radical-induced side reactions. In the absence of antioxidants rapid stereomutation of unsaturated acyl moieties as well as formation of high proportions of thiyl radical-induced addition products such as isomeric 9(10)-S-tetradecyl stearic acids and 9(10)-S-tetradecyl stearic acid tetradecyl thioesters were observed.
Weber
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N
Institute for Biochemistry and Technology of Lipids, H.P. Kaufmann-Institute, Federal Centre for Cereal, Potato and Lipid Research, Münster, Germany. ibtfett@uni-muenster.de
Klein
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E
Vosmann
K
K
Mukherjee
K D
KD
D000975:Antioxidants / Q000737:chemistry*; D002084:Butylated Hydroxytoluene / Q000737:chemistry; D004800:Enzymes, Immobilized; D005231:Fatty Acids, Unsaturated / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000737:chemistry; D005656:Fungal Proteins; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D008041:Linoleic Acids / Q000737:chemistry; D008049:Lipase / Q000737:chemistry*; D008956:Models, Chemical; D009154:Mutation; D019301:Oleic Acid / Q000737:chemistry; D009829:Oleic Acids; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013997:Time Factors; D014466:Ultraviolet Rays
D000975:Antioxidants; D004800:Enzymes, Immobilized; D005231:Fatty Acids, Unsaturated; D016166:Free Radical Scavengers; D005656:Fungal Proteins; D008041:Linoleic Acids; D009829:Oleic Acids; D013438:Sulfhydryl Compounds; C016627:octyl gallate; D002084:Butylated Hydroxytoluene; C005575:methyl linoleate; D019301:Oleic Acid; C011459:elaidic acid; D005707:Gallic Acid; C093666:Lipozyme; C093667:Novozyme 435; D008049:Lipase