1 H NMR ( 400 MHz , CDCl 3 ) δ 8 . 48 ( s , 1 H ) , 7 . 91 ( d , J = 8 . 9 Hz , 1 H ) , 7 . 74 ( d , J = 2 . 2 Hz , 1 H ) , 7 . 40 ( dd , J = 8 . 9 , 2 . 2 Hz , 1 H ) , 4 . 02 ( br dd , J = 12 , 5 Hz , 1 H ) , 3 . 88 ( br s , 2 H ) , 3 . 29 - 3 . 56 ( m , 4 H ) , 1 . 82 - 1 . 96 ( m , 2 H ) , 1 . 56 ( dddd , J = 12 , 12 , 12 , 5 Hz , 1 H ) , 1 . 21 - 1 . 31 ( m , 1 H ) , 1 . 21 ( d , J = 6 . 2 Hz , 3 H ) .