Br.C[O:3][C:4]1[C:5](=[O:23])[C:6]2[C:14](=[CH:15][C:16]=1[O:17]C)[C:13]1[C:8](=[CH:9][C:10]([O:21]C)=[C:11]([O:19]C)[CH:12]=1)[CH:7]=2>C(O)(=O)C>[OH:3][C:4]1[C:5](=[O:23])[C:6]2[C:14](=[CH:15][C:16]=1[OH:17])[C:13]1[C:8](=[CH:9][C:10]([OH:21])=[C:11]([OH:19])[CH:12]=1)[CH:7]=2To a mixed solution of acetic acid (20 ml) and 47% hydrobromic acid (10 ml), 2,3,6,7-tetramethoxyfluorenone (8.0 g) was added and the mixture was refluxed for 15 hours. After cooling, the precipitated crystals were filtered, washed with water and then recrystallized from water-containing ethanol to give 5.0 g of 2,3,6,7-tetrahydroxyfluorenone as a claret powder.
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