Regioselective Hydroxylation of Flavonoids by Transition-Metal-Catalyzed C-H Bond Oxidation.

Regioselective synthesis of 5,6,7-trihydroxyl and 5,7,8-trihydroxyl flavones has been achieved via a transition-metal-catalyzed C-H oxidation as the key step using naturally enriched 5,7-dihydroxyl flavone. The developed chemistry was applied to the synthesis of the naturally occurring and biologically active flavonoids wogonin ( 2 ), oroxylin A ( 3 ), and their glycosylated derivatives ( 4 and 5 ) as potential carnitine palmitoyltransferase 1 activators.