InChI=1/C20H20O4/c1-20(2)8-7-16-18(24-20)6-3-12-9-13(11-23-19(12)16)15-5-4-14(21)10-17(15)22/h3-8,10,13,21-22H,9,11H2,1-2H3/t13-/s2