InChI=1S/C21H20O13/c22-9(3-1-7-2-4-10(23)15(27)14(7)26)13-11(24)5-8(6-12(13)25)33-21-18(30)16(28)17(29)19(34-21)20(31)32/h1-6,16-19,21,23-30H,(H,31,32)/b3-1+