Combined NMR three-bond scalar coupling measurements and QM calculations to calculate OH-rotamer equilibrium of polyalcohols

Authors

  • Katalin E. Kövér,

    1. Department of Inorganic and Analytical Chemistry, University of Debrecen, H-4032 Debrecen, Egyetem tér 1
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  • Tamás Beke,

    1. Protein Modeling Group HAS-ELTE, Institute of Chemistry, Eötvös Loránd University, H-1538, Budapest, P.O.B. 32, Hungary
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  • András Lipták,

    1. Carbohydrate Research Group of the Hungarian Academy of Sciences, University of Debrecen, H-4032 Debrecen, Egyetem tér 1
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  • András Perczel

    Corresponding author
    1. Protein Modeling Group HAS-ELTE, Institute of Chemistry, Eötvös Loránd University, H-1538, Budapest, P.O.B. 32, Hungary
    2. Laboratory of Structural Chemistry and Biology, Institute of Chemistry, Eötvös Loránd University, Pázmány Péter sétány 1/A, H-1117, Budapest, Hungary
    • Protein Modeling Group HAS-ELTE, Institute of Chemistry, Eötvös Loránd University, H-1538, Budapest, P.O.B. 32, Hungary
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Abstract

A combined but independently applied NMR and QM procedure has been used to investigate the conformational properties of the exchangeable hydroxyl protons of polyalcohols. In this study, to demonstrate the applicability of such a strategy, we investigated a simple monosaccharide, i.e. α- and β-anomers of a D-glucopyranoside derivative. The redundant set of experimental vicinal homonuclear and heteronuclear scalar couplings involving the OH-protons obtained for both anomers of our model compound were simultaneously analyzed to yield the preferred OH-rotamer populations and moreover to parametrize a new Karplus-type equation for 3JC(i−1)OH(i) coupling. The populations of the lowest energy conformers and the conformational-averaged coupling constants were independently calculated using the QM approach in both vacuum and chloroform. The similarity of the estimated rotamer populations obtained by two very different techniques and the similarity of the experimental and calculated coupling constants suggest that these approaches can be used in conjunction and in a fully integrated way to determine a more accurate atomic level description of molecular conformers. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009

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