InChI=1S/C21H20O9/c22-13(8-6-11-4-2-1-3-5-11)12-7-9-14(23)15(10-12)29-21-18(26)16(24)17(25)19(30-21)20(27)28/h1-10,16-19,21,23-26H,(H,27,28)/b8-6+