Depending upon the conditions of solvent and temperature, oxidation of the readily accessible 2,3,6,7-tetramethoxy-9,10-dimethylphenanthrene (3) with Na2Cr2O7 gave 2,3,6,7-tetramethoxyphenanthrene-9,10-dicarboxylic acid anhydride (1), 2,2′-diacetyl-4,4′,5,5′-tetramethoxybiphenyl (4), or the new aldehyde 5. Compounds 1 and 4 have been obtained previously only by oxidative degradation of the alkaloid tylophorine (2); their ready availability may be of value for the synthesis of pharmacologically active compounds related to 2.