Synthesis of 5-hydroxy-6- and 8-methylflavones and their ultraviolet spectral differentiation

Article abstract of DOI:10.1016/S0031-9422(97)00919-9

Ultraviolet spectra of fifteen natural or synthetic 6- and 8- methylflavones, with hydroxy group at C-5 and hydroxy or methoxy groups at C- 7, were recorded in methanol and in presence of neutral or acidic aluminium chloride. Several spectral characteristics may be deduced which are typical of the C-methyl group position and distinguish these compounds from their 6- and 8-methoxy homologues. Moreover, for flavones of each the above-mentioned groups, B-ring substitution at C-4', C-3',4' and C-3',4',5' (hydroxy and/or methoxy groups) may be differentiated. On the other hand, spectral differences are unimportant between 8-methylflavones and 8-(p- hydroxybenzyl)flavones, in a similar manner mono- or disubstituted at C-4' or C-3',4'. During this work three 6-methylflavones and four 8-methylflavones were newly synthesized.