Using the more easily accessible 5:7: 8-trihydroxy derivatives of isoflavones a convenient method has been worked out for the synthesis of 5: 6: 7-trihydroxy derivatives. It consists in the alkali fission of 5-hydroxy-7: 8-dimethoxy isoflavone and its 2-methyl derivative to yield 2: 6-dihydroxy-3: 4-dimethoxy-phenyl-benzyl ketone. This ketone on treatment with ethyl formate and sodium yields 5-hydroxy-6 : 7-dimethoxy isoflavone. Vigorous acetylation of the ketone using acetic anhydride and sodium acetate yields 2-methyl-5-hydroxy-6: 7-dimethoxy isoflavone which is compared with an authentic sample prepared by an independent method. 5-Hydroxy-7 : 8-dimethoxy isoflavone yields a small quantity of 5-hydroxy 6: 7-dimethoxy isoflavone during alkali fission.