InChI=1S/C21H20O12/c22-9-3-1-2-8(6-9)4-5-10(23)13-12(7-11(24)14(25)15(13)26)32-21-18(29)16(27)17(28)19(33-21)20(30)31/h1-7,16-19,21-22,24-29H,(H,30,31)/b5-4+