-3.3 and -4.6 ppm for C-1 and C-1′ in the HHDP moiety, respectively, for the α-anomer) (Table ). On the other hand, the calculated 1 H and C NMR chemical shifts of conformers in which all six hydroxy groups point in the same direction and form hydrogen bonding between the 6-and 6'-hydroxy groups (B-type conformers; 2B: the lowest energy conformer in this group) (Figure ) agreed more closely with the experimental data (ΔδC: +2.4 and +1.7 ppm for C-1 and C-1′ in the HHDP moiety, respectively, for the α-anomer) (Table ). However, a discrepancy remained in the calculated chemical shifts at C-3 of the glucose moiety (ΔδH = -0.82 ppm, ΔδC = +5.9 ppm for the α-anomer) (Tables and). This deviation is likely due to conformational changes triggered by intramolecular hydrogen bonding between the 2-hydroxy group and the 3-ester carbonyl. It is known that in DFT calculations, the stabilizing effects of intramolecular hydrogen bonds can be overestimated. In polar solvents such as CD3OD, the 2-hydroxy group is more likely to form hydrogen bonds with the solvent rather than this intramolecular interaction, thus altering the conformation. When the calculations were restricted to conformers lacking that intramolecular hydrogen bond (C-type conformers, 2C: the lowest-energy conformer in this group) (Figure ), the resulting chemical shifts correlated very closely with the experimental values (ΔδH-3 = -0.03 ppm, ΔδC-3 = -1.2 ppm for the α-anomer) (Figure , Tables ). In CD3OD, the 6-and 6′-hydroxy groups of the HHDP moiety are indeed close enough to form an intramolecular hydrogen bond, whereas the 2-hydroxy group of the glucose unit likely forms hydrogen bonding with the solvent. We thus conclude that 2′ is the known monomeric ellagitannin gemin D (2). Calculations were performed at the mPW1PW91/6-311+G(2d,p)//B3LYP/6-31G (d,p) level.