1 H NMR ( DMSO - d 6 , 400 MHz ) δ 8 . 49 ( d , J = 9 . 1 Hz , 1 H ) , 6 . 77 ( d , J = 9 . 1 Hz , 1 H ) , 4 . 27 - 4 . 24 ( m , 1 H ) , 4 . 16 - 4 . 09 ( m , 1 H ) , 4 . 03 ( s , 3 H ) , 3 . 84 - 3 . 80 ( m , 1 H ) , 3 . 27 - 3 . 23 ( m , 1 H ) , 2 . 92 - 2 . 86 ( m , 1 H ) , 2 . 13 - 2 . 07 ( m , 2 H ) , 2 . 01 ( s , 3 H ) , 1 . 69 - 1 . 59 ( m , 1 H ) , 1 . 54 - 1 . 50 ( m , 1 H ) ;