InChI=1S/C23H20O6/c24-19-15-13-18(14-16-19)21-22(29-21)23(27)28-17-11-9-7-5-3-1-2-4-6-8-10-12-20(25)26/h4,6,13-16,21-22,24H,2,8,10,12,17H2,(H,25,26)/b6-4+