1 H NMR ( DMSO d 6 ) δ 9 . 25 ( 1 H , br ) , 8 . 70 ( 1 H , ddd , J = 4 . 9 , 1 . 8 , 1 . 2 Hz ) , 7 . 67 ( 1 H , dd , J = 7 . 9 , 1 . 8 Hz ) , 7 . 64 ( 1 H , d , J = 1 . 8 Hz ) , 7 . 50 - 7 . 42 ( 2 H , m ) , 7 . 39 ( 1 H , d , J = 6 . 7 Hz ) , 5 . 98 ( 1 H , s ) , 4 . 53 ( 1 H , dd , J = 15 . 3 , 6 . 1 Hz ) , 4 . 44 ( 1 H , dd , J = 15 . 3 , 5 . 5 Hz ) , 3 . 35 ( 1 H , d , J = 16 . 5 Hz ) , 3 . 24 ( 1 H , d , J = 16 . 5 Hz ) , 2 . 82 - 2 . 64 ( 2 H , m ) , 2 . 30 - 2 . 17 ( 2 H , m ) .