Regio- and stereoselective synthesis of the major metabolite of quercetin, quercetin-3-O-β-d-glucuronide

Protected quercetin was first transformed selectively in its 3-O-β-d-glucoside. Further protection of the remaining phenolic hydroxyl group allows a clean oxidation of the glucoside by TEMPO/NaOCl/NaBr under phase transfer conditions into the corresponding glucuronide which was cleanly deprotected to quercetin-3-O-β-d-glucuronide.