Reexamination of the published NMR data for 1′ surfaced insight about misassignments in the 1 H, C, and 2D NMR spectra. Notably, the 1 H NMR integral ratio for the α-and βglucopyranose anomers was approximately 1.0:0.9. In the HMBC spectrum, H-2 and H-3 of the glucose moiety showed correlations with the ester carbonyl carbons of the HHDP unit. These features are consistent with the known monomeric ellagitannin 2,3-O-HHDP-glucopyranose. A free anomeric center naturally generates α/β-anomeric isomers, explaining the duplicated NMR signals. Further, naturally occurring ellagitannins bearing a 2,3-HHDP moiety usually possess the (Sa) atropisomer formed by the biaryl axis, whereas the (Ra)-atropisomers are rare. Even more interesting, the reported NMR data for 1′ (recorded in CD3OD) showed good agreement with the literature data for 2,3-O-(Sa)-HHDP-D-glucopyranose (1) (measured in acetone-d6), despite the different solvents used. To confirm our perspective, we compared the 1 H and C NMR spectra of 1′ with those of authentic 1, which was isolated from Castanopsis fissa in our laboratory, in the same solvent (CD3OD). The obtained spectra were in complete agreement (Table ), proving that 1′ is identical to 1. ). This misinterpretation of a dimeric ion cluster explains how monomeric natural products can be interpreted as dimers in mass spectrometric analyses. 17