InChI=1S/C21H20O12/c22-9-6-13(26)15(11(24)4-2-8-1-3-10(23)12(25)5-8)14(7-9)32-21-18(29)16(27)17(28)19(33-21)20(30)31/h1-7,16-19,21-23,25-29H,(H,30,31)/b4-2+