Published in

Elsevier, Carbohydrate Research, (403), p. 149-156, 2015

DOI: 10.1016/j.carres.2014.05.011

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NMR characterization of chemically synthesized branched α-dextrin model compounds

This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Abstract

(1)H and (13)C NMR chemical shifts were accurately determined by consistent referencing for an extensive set of chemically synthesized branched α-glucan model compounds. The model compounds include anomerically fixed and reducing oligosaccharides ranging in size from isomaltose to a doubly branched decasaccharide. Both the (13)C1 chemical shift and the (13)C6 chemical shifts in α-(1→6) glycosidic bonds are strongly dependent on the chemical structure in the vicinity of the branch point, especially on the addition of glucopyranosyl units towards the non-reducing end of the backbone chain. The conformational sampling at the branch point of the branched α-glucan model compounds was experimentally probed with homo-nuclear scalar couplings. Substitution at O6 consistently increases the fraction of C6-O6 trans conformations, but to a lesser extent, if the attachment occurs at the reducing end residue. Increasingly complex structures in the vicinity of the branch point increase the population of the gauche-trans conformation of the C5-C6 bond. This population change is found to correlate with the (13)C6 chemical shift.