InChI=1S/C21H20O11/c22-8-14-17(28)18(29)19(30)21(31-14)32-20-15(12(25)7-13(26)16(20)27)11(24)6-3-9-1-4-10(23)5-2-9/h1-7,14,17-19,21-23,26,28-30H,8H2/b6-3+