FLAVONOIDS OF CITRUS .9. SOME NEW C-GLYCOSYLFLAVONES AND A NUCLEAR MAGNETIC RESONANCE METHOD FOR DIFFERENTIATING 6- AND 8-C-GLYCOSYL ISOMERS

6-C-β-D-Glucopyranosyldiosmetin and 8-C-β-D-glucopyranosyldiosmetin have been isolated from citrus species and their structures determined from nmr and other spectral data. In addition, 2''-O-β-D-xylosylvitexin, a di-C-glycosylapigenin, and a di-C-glycosyldiosmetin have been obtained. The chemical shifts of acetyl methyl bands in the nmr spectra of various acetylated C-glycosyl compounds are discussed. It is shown that these shifts as well as other spectral and chromatographic data can be used to determine the position of substitution of the glucosyl residue. © 1968, American Chemical Society. All rights reserved.