Anhydrous aluminium chloride in ether solution is found to be a convenient reagent for the selective demethylation of the 5-position of methoxy flavanones and these 5-hydroxy compounds can serve as standard derivatives for comparison. A number of typical compounds are reported, the most important being naringenin dimethyl ether, citronetin monomethyl ether and carthamidin and isocarthamidin trimethyl ethers. The method has been employed for the synthesis of dihydrowogonin which has been recently isolated. This involves the preparation and partial demethylation of 7-hydroxy-5:8-dimethoxy flavanone.