1 H NMR ( CDCl 3 ) δ 8 . 70 ( 1 H , dt , J = 4 . 7 , 1 . 6 Hz ) , 7 . 57 ( 1 H , d , J = 7 . 6 Hz ) , 7 . 46 ( 1 H , d , J = 2 . 0 Hz ) , 7 . 19 - 7 . 35 ( 6 H , m ) , 6 . 04 ( 1 H , br s ) , 4 . 53 - 4 . 64 ( 2 H , m ) , 4 . 39 ( 1 H , d , J = 16 . 8 Hz ) , 4 . 28 ( 1 H , d , J = 15 . 2 Hz ) , 4 . 19 ( 1 H , dd , J = 12 . 5 , 1 . 5 Hz ) , 3 . 43 ( 1 H , dd , J = 12 . 5 , 3 . 9 Hz ) , 2 . 56 - 2 . 64 ( 1 H , m ) , 2 . 29 - 2 . 53 ( 3 H , m ) .