InChI=1S/C21H20O4/c1-12-11-15(21-16(22)6-4-8-19(21)25-12)13-9-10-17(23)20-14(13)5-3-7-18(20)24-2/h3-10,12,15,22-23H,11H2,1-2H3/t12-,15?/m0/s1