InChI=1S/C21H20O9/c22-12-7-9-15(13(10-12)14(23)8-6-11-4-2-1-3-5-11)29-21-18(26)16(24)17(25)19(30-21)20(27)28/h1-10,16-19,21-22,24-26H,(H,27,28)/b8-6+