InChI=1S/C21H28O6/c1-19(2)11-16(22)12-21(19,4)15-7-5-14(6-8-15)18(25)27-10-9-20(3,26)13-17(23)24/h5-8,26H,9-13H2,1-4H3,(H,23,24)/t20-,21-/m1/s1