InChI=1S/C20H28O4/c1-3-4-5-13(2)18(21)8-7-16-17-11-14(6-9-20(23)24)10-15(17)12-19(16)22/h6-8,13,15-19,21-22H,5,9-12H2,1-2H3,(H,23,24)/b8-7+,14-6+/t13?,15-,16+,17-,18+,19+/m0/s1