1 H NMR ( CDCl 3 ) δ 8 . 60 ( 1 H , br dd , J = 4 . 6 , 1 . 3 Hz ) , 7 . 70 ( 1 H , d , J = 7 . 9 Hz ) , 7 . 65 ( 1 H , d , J = 7 . 3 Hz ) , 7 . 47 ( 1 H , br dd , J = 7 . 9 , 1 . 3 Hz ) , 7 . 40 ( 1 H , dd , J = 7 . 9 , 7 . 3 Hz ) , 7 . 30 ( 1 H , br ) , 7 . 18 ( 1 H , dd , J = 7 . 9 , 4 . 6 Hz ) , 6 . 35 ( 1 H , br s ) , 5 . 31 ( 1 H , d , J = 2 . 6 Hz ) , 4 . 73 ( 2 H , d , J = 5 . 9 Hz ) , 2 . 88 - 2 . 83 ( 2 H , m ) , 2 . 60 - 2 . 20 ( 2 H , m ) .