Conformation analysis ofd-glucaric acid in deuterium oxide by NMR based on itsJHHandJCHcoupling constants

Autor:	Tetsuya Ito, Tadahisa Iwata, Kazuo Furihata, Hisaharu Masaki, Yukiko Enomoto-Rogers
Rok vydání:	2016
Předmět:	Aldaric acid 010405 organic chemistry Chemistry Stereochemistry General Chemistry Nuclear magnetic resonance spectroscopy Nuclear Overhauser effect 010402 general chemistry 01 natural sciences Glucaric Acid 0104 chemical sciences chemistry.chemical_compound Heteronuclear molecule Deuterium General Materials Science Conformational isomerism Two-dimensional nuclear magnetic resonance spectroscopy
Zdroj:	Magnetic Resonance in Chemistry. 54:561-567
ISSN:	0749-1581
DOI:	10.1002/mrc.4396
Popis:	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) JHH ) and proton-carbon ((2) JCH and (3) JCH ) coupling constants, as well as nuclear overhauser effect spectroscopy (NOESY). The (2) JCH and (3) JCH 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., C2C3, C3C4, and C4C5) 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.
Databáze:	OpenAIRE
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