- Use of Shift Reagent with MTPA Derivatives in 19F NMR Spectroscopy IV - Determination of Enantiomeric Composition for a Variety of Secondary Cycloalkanols. A Survey
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Chiral secondary cycloalkanols (monpocyclic alcohols) are derivatized to the corresponding (R)-α-methoxy-α-trifluoromethyl-α-phenylacetic acid esters and analysed by 19F NMR in the presence of tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III) .Using this method the enantiomeric composition can be measured for severak cyclopentanols, cyclohexanols and cycloheptanols, with a variety of substitution patterns.It is shown that a mixture of four stereoisomeric cycloalkanols, such as cis and trans disubstituted alcohols, can be analysed simultaneously.
- Merckx, E. M.,Lepoivre, J. A.,Lemiere, G. L.,Alderweireldt, F. C.
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p. 380 - 387
(2007/10/02)
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- ENZYMATIC "IN VITRO" REDUCTION OF KETONES. VI.(1) Reduction rates and stereochemistry of the HLAD-catalyzed reduction of 3-alkyl- and 4-alkylcyclohexanones.
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Reaction rate constants for the catalytic step HLAD-NADH + ketone * HLAD-NAD+ + alcohol in the HLAD-catalyzed reduction of 3-alkyl- and 4-alkylcyclohexanones are determined from initial rate measurements in the coenzyme recycling system ketone-ethanol-NAD+-HLAD.By rate measurements at several temperatures, activation parameters were determined and isokinetic relationships tracked down.Two different isokinetic relationships show that the 3-alkylcyclohexanones pass through an other type of transition state than cyclohexanone and the 4-alkylcyclohexanones, which means that they have a different arrangement on the HLAD-NADH complex.The results are rationalized in view of the most recent principles on nucleophilic additions to carbonyl functions.The resulting model for the HLAD-catalyzed reduction adequately explains the observed rate accelerating and decelerating effects and the stereochemistry of the reduction as well.
- Osselaer, T. A. Van,Lemiere, G. L.,Lepoivre, J. A.,Alderweireldt, F. C.
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p. 133 - 150
(2007/10/02)
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