1 H NMR ( DMSO - d 6 , 400 MHz ) δ 8 . 56 ( d , J = 8 . 9 Hz , 1 H ) , 7 . 33 - 7 . 31 ( m , 3 H ) , 7 . 21 - 7 . 20 ( m , 2 H ) , 7 . 13 ( d , J = 8 . 96 Hz , 1 H ) , 4 . 52 ( d , J = 12 . 8 Hz , 1 H ) , 4 . 09 ( d , J = 12 . 8 Hz , 1 H ) , 3 . 90 ( s , 3 H ) ;