InChI=1S/C21H22O6/c1-13(2)11-18(24)27-21-16(23)12-17(26-3)19(20(21)25)15(22)10-9-14-7-5-4-6-8-14/h4-10,12-13,23,25H,11H2,1-3H3/b10-9+