Characterization of d-glucaric acid using NMR, X-ray crystal structure, and mm3 molecular modeling analyses

d-Glucaric acid was characterized in solution by comparing NMR spectra from the isotopically unlabeled molecule with those from d-glucaric acid labeled with deuterium or carbon-13 atoms. The NMR studies provided unequivocal assignments for all carbon atoms and non-hydroxyl protons of the molecule. The crystal structure of d-glucaric acid was obtained by X-ray diffraction techniques and the structure was a close match to the low energy conformation generated from a Monte-Carlo-based searching protocol employing the mm3 molecular mechanics program. The molecule adopts a bent structure in both the crystalline and computationally generated lowest-energy structure, a conformation that is devoid of destabilizing eclipsed 1,3-hydroxyl interactions.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We employ NMR and X-ray diffraction techniques to characterize d-glucaric acid in aqueous solution and in the crystalline state, respectively. ► Molecular modeling analyses are employed to evaluate the conformational distribution of d-glucaric acid. ► 1H and 13C NMR assignments of d-glucaric acid are supported by spectral assignments from deuterium and carbon 13 labeled d-glucaric acid. ► Crystalline d-glucaric acid has a sickle conformation. ► The lowest energy computationally generated conformation of d-glucaric acid is a close match to its crystal structure.