1 H NMR ( CDCl 3 ) δ 8 . 61 ( 1 H , dt , J = 4 . 7 , 1 . 6 Hz ) , 7 . 51 ( 1 H , dt , J = 7 . 8 , 1 . 5 Hz ) , 7 . 40 ( 1 H , dd , J = 8 . 5 , 6 . 1 Hz ) , 7 . 14 - 7 . 25 ( 3 H , m ) , 6 . 99 ( 1 H , td , J = 8 . 3 , 2 . 6 Hz ) , 4 . 51 - 4 . 68 ( 2 H , m ) , 3 . 76 ( 2 H , dd , J = 9 . 5 , 8 . 4 Hz ) , 3 . 34 - 3 . 37 ( 4 H , m ) , 2 . 57 - 2 . 72 ( 1 H , m ) , 2 . 38 - 2 . 49 ( 1 H , m ) 2 . 18 - 2 . 32 ( 2 H , m ) .