1 H 　 NMR ( DMSO - d 6 , 400 MHz ) δ 10 . 33 ( s , 1 H ) , 9 . 66 ( s , 1 H ) , 9 . 18 ( s , 1 H ) , 7 . 82 - 7 . 75 ( m , 3 H ) , 7 . 70 - 7 . 68 ( m , 3 H ) , 7 . 01 ( d , J = 8 Hz , 2 H ) , 3 . 76 ( t , J = 4 Hz , 4 H ) , 3 . 09 ( t , J = 4 Hz , 4 H ) , 2 . 55 ( s , 3 H ) .