Six flavonoid 7-O-β-D-glycosides 1a-3a and 1b–3b were synthesised from the flavones 7a and 7b by glycosidation and deacetylation with the corresponding α-acetylglycosyl bromides. 7a and 7b were prepared in high yield by an improved Baker-Venkataraman rearrangement using 2, 4-dihydroxyacetophenone as starting material and tetrabutylammonium bromide (TBAB) as a phase transfer catalyst. The glycosidation procedure was modified by using anhydrous K2CO3 in a solvent mixture of DMF/acetone (3:2v/v) and TBAB as a phase transfer catalyst.
FurnissB.S., HannafordA. J., and SmithP. W. G., TatchellA. R.Textbook of practical organic chemistry, 5th edn, with John Wilcy&Sons, New York, 1989, 647.
