InChI=1S/C19H20O6S/c20-17(10-5-16-6-11-18(21)12-7-16)4-2-1-3-15-8-13-19(14-9-15)25-26(22,23)24/h2,4,6-9,11-14,21H,1,3,5,10H2,(H,22,23,24)/b4-2+