A SIMPLE SYNTHESIS OF C-13(6)-LABELED FLAVONE AND 5-METHOXYFLAVONE

The C-13(6)-labelled molecules, flavone and 5-methoxyflavone, with the carbon-13 label at all six carbons of the aromatic B ring, have been prepared for use as internal standards in isotope dilution-mass spectrometry. The key step involves addition of a labelled benzoyl group to the methyl group of a hydroxyacetophenone, forming a 1,3-diketone. Overall yields from C-13(6)-benzoic acid were 38% for the labelled flavone and 45% for the labelled 5-methoxyflavone.