NMR characterization of chemically synthesized branched α-dextrin model compounds

Bent O. Petersen, Mohammed Saddik Motawie, Birger Lindberg Møller, Ole Hindsgaul, Sebastian Meier

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

1H and 13C NMR chemical shifts were accurately determined by consistent referencing for an extensive set of chemically synthesized branched a-glucan model compounds. The model compounds include anomerically fixed and reducing oligosaccharides ranging in size from isomaltose to a doubly branched decasaccharide. Both the 13C1 chemical shift and the 13C6 chemical shifts in a−(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 a-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 13C6 chemical shift.
Original languageEnglish
JournalCarbohydrate Research
Number of pages24
ISSN0008-6215
DOIs
Publication statusAccepted/In press - 2014
Externally publishedYes

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