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Conformation analysis of d ‐glucaric acid in deuterium oxide by NMR based on its J HH and J CH coupling constants
Author(s) -
EnomotoRogers Yukiko,
Masaki Hisaharu,
Ito Tetsuya,
Furihata Kazuo,
Iwata Tadahisa
Publication year - 2016
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.4396
Subject(s) - conformational isomerism , chemistry , heteronuclear molecule , two dimensional nuclear magnetic resonance spectroscopy , nuclear overhauser effect , nuclear magnetic resonance spectroscopy , proton , crystallography , spectroscopy , deuterium , coupling constant , j coupling , stereochemistry , nuclear magnetic resonance , molecule , organic chemistry , physics , particle physics , quantum mechanics
d ‐Glucaric acid (GA) is an aldaric acid and consists of an asymmetric acyclic sugar backbone with a carboxyl group positioned at either end of its structure (i.e., the C1 and C6 positions). The purpose of this study was to conduct a conformation analysis of flexible GA as a solution in deuterium oxide by NMR spectroscopy, based on J ‐resolved conformation analysis using proton–proton ( 3 J HH ) and proton–carbon ( 2 J CH and 3 J CH ) coupling constants, as well as nuclear overhauser effect spectroscopy (NOESY). The 2 J CH and 3 J CH coupling constants were measured using the J ‐resolved heteronuclear multiple bond correlation (HMBC) NMR technique. NOESY correlation experiments indicated that H2 and H5 were in close proximity, despite the fact that these protons were separated by too large distance in the fully extended form of the chain structure to provide a NOESY correlation. The validities of the three possible conformers along the three different bonds (i.e., C2C3, C3C4, and C4C5) were evaluated sequentially based on the J ‐coupling values and the NOESY correlations. The results of these analyses suggested that there were three dominant conformers of GA, including conformer 1 , which was H2H3:gauche, H3H4:anti, and H4H5:gauche; conformer 2 , which was H2H3:gauche, H3H4:anti, and H4H5:anti; and conformer 3 , which was H2H3:gauche, H3H4: gauche, and H4H5:anti. These results also suggested that all three of these conformers exist in equilibrium with each other. Lastly, the results of the current study suggested that the conformational structures of GA in solution were ‘bent’ rather than being fully extended. Copyright © 2016 John Wiley & Sons, Ltd.