InChI=1S/C21H20O11/c22-7-15-18(27)19(28)20(29)21(32-15)30-9-5-12(25)16-13(6-9)31-14(17(16)26)4-8-1-2-10(23)11(24)3-8/h1-6,15,18-25,27-29H,7H2/b14-4+