Experimental and computational studies of nJ(77Se, 1H) selenium-proton couplings in selenoglycosides |
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Authors: | Kövér Katalin E Kumar Ambati Ashok Rusakov Yury Yu Krivdin Leonid B Illyés Tünde-Zita Szilágyi László |
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Institution: | Department of Chemistry, University of Debrecen, Debrecen, Hungary. kover@tigris.unideb.hu |
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Abstract: | Selenoglycosides are important starting materials in synthetic carbohydrate chemistry and play a role in biological interactions as well. Both aspects are influenced by the conformation around the glycosidic bond. Here, we present a combined experimental and computational approach to measure and evaluate (n)J((77)Se, (1)H) coupling constants for their use in conformational analysis. The measurements were carried out using a modified CPMG-HSQMBC pulse scheme which yields pure absorption antiphase multiplets to allow accurate determination of the (n)J(XH) values regardless of the size of the proton-proton couplings. Theoretical calculations were performed at the Second-Order Polarization Propagator Approach (SOPPA) level. Population-averaged values calculated for geminal and vicinal couplings are in a good agreement with experiment indicating an adequate theoretical level of the calculations. Experimental observations and computations alike have indicated that two-bond (77)Se-(1)H couplings, (2)J((77)Se, (1)H), in a H1-C1-Se-X moiety are very sensitive to the torsion angle around the C1-Se-bond and will, therefore, be useful for conformational studies. |
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