Scope and limitations of the simple 13C-n.m.r. method of structural analysis of carbohydrates: glucodisaccharides |
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| Institution: | 1. Chemistry Department, University of Pretoria, Private Bag X20, Hatfield 0028, Pretoria, South Africa;2. Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa;1. College of Physics, Qingdao University, Qingdao 266071, PR China;2. Key Laboratory of Photonics Materials and Technology in Universities of Shandong, Qingdao University, Qingdao 266071, China;1. CSIRO Animal Health and Food Science, F.D McMaster Laboratory, Armidale NSW 2350, Australia;2. School of Science and Technology, University of New England, Armidale NSW 2350, Australia;1. Department of Chemistry, Garware Research Centre, University of Pune, Pune 411007, India;2. Division of Biochemistry, Department of Chemistry, University of Pune, Pune 411007, India;1. Department of Chemistry and Graduate School Chemical Biology, University of Konstanz, D-78457 Konstanz, Germany;2. Chemical Biology of Carbohydrates, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), D-66123 Saarbrücken, Germany;3. Deutsches Zentrum für Infektionsforschung (DZIF), Standort Hannover-Braunschweig, Germany |
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| Abstract: | The scope and limitations of the SIMPLE n.m.r. method (secondary isotope multiplet n.m.r. spectroscopy of partially labelled entities) has been investigated for a series of glucodisaccharies. 13C-SIMPLE n.m.r. measurements have been made on solutions of (1→1)- (α,α-trehalose), (1→2)- (sophorose and kojibiose), (1→3)- (laminaribiose), and (1→6)-linked (gentiobiose and isomaltose) glucodisaccharides in (CD3)2SO and the results combined with those previously published for (1→4)-linked analogues (maltose and cellobiose). Each linkage (and substitution) type gives rise to a unique pattern of 13C isotopomers which, in principle, may be used for complete assignment of the spectra and structural analysis of the molecule. The glucodisaccharides are difficult to analyse, compared with other disaccharides, because the presence of two glucose moieties leads to degeneracies of a few isotopic multiplets which cannot be differentiated by the magnitudes of the isotope effects. Assignments in aqueous solutions were obtained by using the DIS (differential isotope shift) n.m.r. method in conjunction with the results from SIMPLE n.m.r. In practice, nearly all of the signals can be assigned unequivocally and the remaining signals are choices between two possible assignments. |
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