InChI=1S/C20H28O4/c1-6-13(3)19(21)23-17-11-16-15(5)20(22)24-18(16)10-12(2)8-7-9-14(17)4/h9-10,13,16-18H,5-8,11H2,1-4H3/b12-10+,14-9+