Complete Proton and Carbon Assignment of (+)-Catechin via One- and Two-Dimensional Nuclear Magnetic Resonance (NMR) Analysis

Students from an upper-division undergraduate organic class analyzed one- and two-dimensional 400-MHz NMR spectral data from (+)-catechin hydrate in acetone-d6. Guided assignment of all proton and carbon signals was completed via 1-D proton and carbon, nuclear Overhauser effect (nOe), distorsionless enhancement by polarization transfer (DEPT) 135, 1H–1H correlation spectroscopy (COSY), 1H–13C heteronuclear single quantum coherence (HSQC), and 1H–13C heteronuclear multiple bond coherence (HMBC) NMR experiments. Coupling constants for the aliphatic region were compared to the theoretical values as determined by the Karplus equation and vicinal angles as ascertained by molecular modeling of (+)-catechin. Carbon-13 signals for the aromatic and aliphatic regions were compared to calculated values obtained from both spectroscopic analyses books and computer software.