InChI=1S/C16H20N2O3/c1-6-11-9(3)13(17-15(11)20)8-16(21-5)12(7-2)10(4)14(19)18-16/h7-8H,2,6H2,1,3-5H3,(H,17,20)(H,18,19)/b13-8-