SYNTHESIS OF 5-HYDROXY-6-METHYLFLAVONES AND 8-METHYLFLAVONES AND THEIR ULTRAVIOLET SPECTRAL DIFFERENTIATION

Ultraviolet spectra of fifteen natural or synthetic 6- and 8-methylfla vones; 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 alumin ium chloride. Several spectral characteristics may be deduced which ar e typical of the C-methyl group position and distinguish these compoun ds from their 6-and 8-methoxy homologues. Moreover, for flavones of ea ch the above-mentioned groups, B-ring substitution at C-4', C-3',4' an d C-3',4',5' (hydroxy and/or methoxy groups) may be differentiated. On the other hand, spectral differences are unimportant between 8-methyl flavones and 8-(p-hydroxybenzyl)flavones, in a similar manner mono- or disubstituted at C-4' or C-3',4'. During this work three 6-methylflav ones and four 8-methylflavones were newly synthesized. (C) 1998 Elsevi er Science Ltd. All rights reserved.