Efficient synthesis of polyoxygenated flavones from naturally occurring flavanones.

Flavonoids are constituents of the human diet (they are present in many beverages and food), and in organisms they are responsible for several biological functions, including that of antioxidant. Because of the increasing interest in these molecules, methods for their synthesis and structural modification are of great importance; studies on the biological activities of many of these compounds are insufficient because of their scarcity and/or high cost. We have developed an expeditious synthesis of polyoxygenated flavones, starting from available and inexpensive flavanones, using a bromination-methoxylation procedure. A series of flavonoids that are not otherwise accessible can be prepared using this method. As an example, 3'-demethoxysudachitin, a limited flavone possessing antimicrobial activity against methicillin-resistant Staphylococcus aureus and Helicobacter pylori and acting as a 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenger, was prepared in fairly satisfactory yield.