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High‐resolution 13C NMR studies of proanthocyanidin polymers (condensed tannins)

High‐resolution 13C NMR spectra of some proanthocyanidin polymers are presented. They were measured in acetone‐d6‐water (1:1, v/v) solution at 30 °C and at 62.5 MHz. The chemical shifts of selected resonances in these spectra were compared with those of structurally related monomers and oligomers. These comparisons enable certain deductions to be made regarding the stereochemistry and mode of linkage of the constituent flavanoid monomer units of these polymers.