InChI=1S/C20H18O8/c1-26-14-9-11(4-5-13(14)21)18-17(20(24)25)12-7-10(3-6-16(22)23)8-15(27-2)19(12)28-18/h3-9,17-18,21H,1-2H3,(H,22,23)(H,24,25)/b6-3+