Complete assignments of the 1H and 13C chemical shifts and JH,H coupling constants in NMR spectra of d-glucopyranose and all d-glucopyranosyl- d-glucopyranosides

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Complete assignment of the 1H and 13C NMR spectra of all possible d-glucopyranosyl- d-glucopyranosides was performed and the 1H chemical shifts and proton–proton coupling constants were refined by computational spectral analyses (using PERCH NMR software) until full agreement between the calculated and experimental spectra was achieved. To support the experimental results, the 1H and 13C chemical shifts and the spin–spin coupling constants between the non-hydroxyl protons of α- and β- d-glucopyranose ( 1a and 1b) were calculated with density functional theory (DFT) methods at the B3LYP/pcJ-2//B3LYP/6-31G(d,p) level of theory. The effects of different glycosidic linkage types and positions on the glucose ring conformations and on the α/β-ratio of the reducing end hydroxyl groups were investigated. Conformational analyses were also performed for anomerically pure forms of methyl d-glucopyranosides ( 13a and 13b) and fully protected derivatives such as 1,2,3,4,6-penta- O-acetyl- d-glucopyranoses ( 14a and 14b).