C-13 NMR OF FLAVONOIDS .2. FLAVONOIDS OTHER THEN FLAVONE AND FLAVONOL AGLYCONES

13C NMR spectra for a number of dihydroflavones, dihydroflavonols, flavans, chalcones, flavonols, an isoflavone and several glycosides in DMSO[dimethylsulfide]-d6 solvent are reported and analyzed. The use of established substitution additivity rules and 13C-1H coupling constants together with suitable model compounds permitted near complete, self-consistent interpretations of these spectra. Sites of C-methylation and glycosylation are readily determined as is the interglycosidic linkage within the disaccharide of flavonoid O-diglycosides. Stereochemical effects are observed in the spectra of the dihydro-flavonoids and some flavonol 3-O-glycosides.