1 H NMR ( DMSO d 6 ) δ 9 . 30 ( 1 H , br s ) , 8 . 76 ( 1 H , d , J = 4 . 8 Hz ) , 7 . 79 ( 1 H , s ) , 7 . 71 ( 1 H , d , J = 8 . 2 Hz ) , 7 . 64 ( 1 H , d , J = 2 . 1 Hz ) , 7 . 54 ( 1 H , t , J = 6 . 2 Hz ) , 7 . 47 ( 1 H , d , J = 8 . 1 Hz ) , 7 . 40 ( 1 H , d , J = 8 . 1 Hz ) , 4 . 40 - 4 . 53 ( 2 H , m ) , 4 . 16 ( 1 H , d , J = 8 . 2 Hz ) , 3 . 45 ( 1 H , d , J = 8 . 7 Hz ) , 2 . 57 - 2 . 68 ( 1 H , m ) , 2 . 39 - 2 . 45 ( 1 H , m ) , 2 . 24 - 2 . 38 ( 2 H , m ) .