Two‐dimensional NMR spectra of hydrolysable tannins which form equilibrium mixtures

The structures of hydrolysable tannins, each existing as an equilibrium mixture due to tautomerization at the sugar core(s) or at the dehydrohexahydroxydiphenoyl group (five‐ and six‐membered hemiacetal forms) in the molecule, were elucidated by NMR, employing 2D NMR techniques (COSY, NOESY, 1 H 13 C long‐range COSY, etc.), on derivatives which avoid the spectral complication due to equilibration.