InChI=1S/C21H20O7/c1-3-27-18-17(14-6-10-16(23)11-7-14)21(20(25)26-2,28-19(18)24)12-13-4-8-15(22)9-5-13/h4-11,22-23H,3,12H2,1-2H3/t21-/m1/s1