InChI=1S/C21H20O7/c1-26-19-11-14(4-8-17(19)23)3-7-16(22)13-28-21(25)10-6-15-5-9-18(24)20(12-15)27-2/h3-12,23-24H,13H2,1-2H3/b7-3+,10-6+