InChI=1S/C21H28O9/c1-2-3-11-15(12-9-7-5-4-6-8-10-14(23)13-22)29-21-18(26)16(24)17(25)19(30-21)20(27)28/h1,9,12-19,21,23-26H,4-8,10H2,(H,27,28)/b12-9+