1 H NMR ( CDCl 3 ) δ 8 . 63 ( 1 H , ddd , J = 4 . 3 , 1 . 8 , 1 . 2 Hz ) , 7 . 68 ( 1 H , dd , J = 7 . 9 , 1 . 8 Hz ) , 7 . 24 ( 1 H , ddd , J = 7 . 9 , 4 . 3 , 1 . 8 Hz ) , 6 . 37 ( 1 H , br s ) , 5 . 31 ( 1 H , d , J = 1 . 2 Hz ) , 3 . 81 ( 3 H , s ) , 2 . 89 - 2 . 73 ( 2 H , m ) , 2 . 48 ( 1 H , m ) , 2 . 32 ( 1 H , m ) .