InChI=1S/C20H18O7/c1-10(8-21)2-4-13-16(24)7-17(25)18-19(26)14(9-27-20(13)18)12-5-3-11(22)6-15(12)23/h2-3,5-7,9,21-25H,4,8H2,1H3/b10-2+