1 H NMR ( DMSO d 6 ) δ 8 . 90 ( 1 H , br t , J = 6 . 6 Hz ) , 8 . 49 ( 1 H , dd , J = 4 . 6 , 2 . 0 Hz ) , 7 . 78 ( 1 H , br d , J = 7 . 9 Hz ) , 7 . 67 - 7 . 54 ( 3 H , m ) , 7 . 29 ( 1 H , dd , J = 7 . 9 , 4 . 6 Hz ) , 6 . 43 ( 1 H , s ) , 6 . 18 ( 1 H , br s ) , 5 . 17 ( 1 H , br s ) , 4 . 47 ( 2 H , d , J = 6 . 6 Hz ) , 2 . 78 ( 2 H , m ) , 2 . 23 ( 1 H , m ) , 1 . 96 ( 1 H , m ) .