1 H NMR ( 400 MHz , CDCl 3 ) δ 8 . 84 ( s , 1 H ) , 8 . 29 ( d , J = 1 . 5 Hz , 1 H ) , 8 . 11 ( d , J = 8 . 8 Hz , 1 H ) , 8 . 08 ( br s , 1 H ) , 7 . 80 ( dd , J = 8 . 8 , 1 . 5 Hz , 1 H ) , 7 . 56 ( s , 1 H ) , 5 . 34 ( s , 2 H ) , 4 . 77 ( br d , J = 10 . 8 Hz , 1 H ) , 4 . 30 - 4 . 17 ( m , 1 H ) , 3 . 10 ( dd , J = 9 . 8 , 6 . 4 Hz , 1 H ) , 3 . 07 - 2 . 95 ( m , 2 H ) , 2 . 68 ( ddd , J = 9 . 8 , 5 . 9 , 2 . 0 Hz , 1 H ) , 2 . 42 ( s , 3 H ) , 2 . 40 ( s , 3 H ) .