Browsing by Author "Barth, Stefan"

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    Kinetic analysis and simulation studies for lipase-catalysed resolution of racemic 2-methyl-1-pentanol
    (1993) Indlekofer, Michael; Reuss, Michael; Barth, Stefan; Effenberger, Franz
    The lipase-catalysed optical resolution of a racemic mixture of 2-methyl-1-pentanol by transesterification using vinyl acetate as acyl donor has been studied experimentally. A mechanistic model has been developed for the double-substrate reaction sequence treating both enantiomers as competing substrates. The model is based upon a ping-pong mechanism with alternative substrates involving an acyl-enzyme intermediate. The kinetic constants of the model have been evaluated using initial rate experiments and nonlinear regression analysis. The model successfully predicts the evolution of the enantiomeric excess of substrate (eeR) and the degree of conversion with time for batch experiments with various initial concentrations of vinyl acetate and (R,S)-2-methyl-1-pentanol. Furthermore, the rate equations have been used to theoretically study the dynamic progression of a continuous enzyme-catalysed resolution process. The enantiomeric excess as a function of conversion for different process configurations is discussed. It is found, that the maximum attainable eeR is strongly dependent on the residence time distribution of the continuous reactor and is rather low for a continuous stirred tank reactor (CSTR) due to competitive inhibition effects.
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    Lipase-catalyzed resolution of racemic 2-aklyl substituted 1-alkanols
    (1993) Barth, Stefan; Effenberger, Franz
    (R)-2-alkyl-1-alkanoids (R)-1 with high optical purities were obtained by lipase-catalyzed esterification of the racemic substrates (R,S)-1 with vinyl acetate in dichloromethane. The alcohols (R)-1 were oxidized without racemization to the corresponding carboxylic acids (R)-4. The enriched (S)-acetates (S)-3 either were saponified to the alcohols (S)-1 which are substrates for a second lipase-catalyzed transesterification to give (S)-1 in high optical purity or were racemized and applied once again in the kinetic resolution to prepare (R)-1.