InChI=1S/C21H20O8/c22-15(11-6-12-4-2-1-3-5-12)13-7-9-14(10-8-13)28-21-18(25)16(23)17(24)19(29-21)20(26)27/h1-11,16-19,21,23-25H,(H,26,27)/b11-6+