1 H NMR ( 300 MHz , DMSO - d 6 ) δ 9 . 07 ( s , 1 H ) , 8 . 93 ( s , 1 H ) , 7 . 90 ( d , 2 H , J = 8 . 6 Hz ) , 7 . 62 ( d , 2 H , J = 8 . 8 Hz ) , 7 . 50 ( d , 2 H , J = 8 . 8 Hz ) , 7 . 33 ( d , 2 H , J = 8 . 8 Hz ) , 3 . 13 ( t , 2 H , J = 7 . 2 Hz ) , 2 . 74 ( t , 2 H , J = 7 . 2 Hz ) , 2 . 38 ( m , 4 H ) , 1 . 44 ( m , 4 H ) , 1 . 35 ( m , 2 H ) ; MS ( m / z ) : 425 ( M +).