InChI=1S/C20H20O8/c1-26-17-7-4-12(9-16(17)23)5-8-19(24)28-18(20(25)27-2)11-13-3-6-14(21)15(22)10-13/h3-10,18,21-23H,11H2,1-2H3/b8-5+/t18-/m1/s1