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NMR analysis of conformationally dependent n J C, H and n J C, C in the trisaccharide α‐L‐Rha p ‐(1 → 2)[α‐L‐Rha p ‐(1 → 3)]‐α‐L‐Rha p ‐OMe and a site‐specifically labeled isotopologue thereof
Author(s) -
Jonsson K. Hanna M.,
Pendrill Robert,
Widmalm Göran
Publication year - 2011
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2723
Subject(s) - chemistry , trisaccharide , coupling constant , stereochemistry , nuclear magnetic resonance spectroscopy , nmr spectra database , proton nmr , proton , two dimensional nuclear magnetic resonance spectroscopy , j coupling , carbon 13 nmr , crystallography , relaxation (psychology) , spectral line , analytical chemistry (journal) , organic chemistry , physics , psychology , particle physics , quantum mechanics , astronomy , social psychology
An array of NMR spectroscopy experiments have been carried out to obtain conformationally dependent 1 H, 13 C‐ and 13 C, 13 C‐spin–spin coupling constants in the trisaccharide α‐ L ‐Rha p ‐(1 → 2)[α‐ L ‐Rha p ‐(1 → 3)]‐α‐ L ‐Rha p ‐OMe. The trisaccharide was synthesized with 13 C site‐specific labeling at C2′ and C2″, i.e. in the rhamnosyl groups in order to alleviate 1 H spectral overlap. This facilitated the measurement of a key trans ‐glycosidic proton–proton cross‐relaxation rate using 1D 1 H, 1 H‐T‐ROESY experiments as well as a 3 J C, H coupling employing 1D 1 H, 13 C‐long‐range experiments, devoid of potential interference from additional J coupling. By means of both the natural abundance compound and the 13 C‐labeled sample 2D 1 H, 13 C‐J‐HMBC and 1 H, 13 C‐HSQC‐HECADE NMR experiments, total line‐shape analysis of 1 H NMR spectra and 1D 13 C NMR experiments were employed to extract 3 J C, H , 2 J C, H , 3 J C, C , and 1 J C, C coupling constants. The 13 C site‐specific labeling facilitates straightforward determination of n J C, C as the splitting of the 13 C natural abundance resonances. This study resulted in eight conformationally dependent coupling constants for the trisaccharide and illustrates the use of 13 C site‐specific labeling as a valuable approach that extends the 1D and 2D NMR methods in current use to attain both hetero‐ and homonuclear spin–spin coupling constants that subsequently can be utilized for conformational analysis. Copyright © 2011 John Wiley & Sons, Ltd.