InChI=1S/C22H20O6/c1-22(2)9-8-14-17(28-22)11-19(25-3)20(21(14)24)15(23)6-4-13-5-7-16-18(10-13)27-12-26-16/h4-11,24H,12H2,1-3H3/b6-4+