InChI=1S/C21H16O7/c1-21(2)4-3-9-13(28-21)6-11-18-16(20(23)27-19(11)17(9)22)10-5-14-15(25-8-24-14)7-12(10)26-18/h5-7,22H,3-4,8H2,1-2H3