InChI=1S/C18H18N2O4/c1-9-11(6-7-16(22)23)10(2)19-14(9)8-13-12-4-3-5-15(21)17(12)20-18(13)24/h3-5,8,19,21H,6-7H2,1-2H3,(H,20,24)(H,22,23)/b13-8-