1 H - NMR ( 400 MHz , DMSO - d 6 ) δ : 8 . 03 ( 1 H , t , J = 6 . 0 Hz ) , 7 . 63 ( 1 H , s ) , 7 . 57 ( 1 H , d , J = 8 . 0 Hz ) , 7 . 44 - 7 . 42 ( 1 H , m ) , 7 . 39 - 7 . 37 ( 1 H , m ) , 7 . 32 - 7 . 25 ( 2 H , m ) , 6 . 90 ( 1 H , d , J = 8 . 4 Hz ) , 4 . 63 ( 2 H , t , J = 8 . 8 Hz ) , 4 . 02 ( 2 H , d , J = 6 . 4 Hz ) , 3 . 23 ( 2 H , t , J = 8 . 8 Hz ) .