1 H - NMR ( 400 MHz , DMSO - d 6 ) δ : 7 . 90 ( 2 H , d , J = 8 . 8 Hz ) , 7 . 72 ( 2 H , d , J = 8 . 8 Hz ) , 7 . 39 ( 4 H , m ) , 7 . 15 ( 1 H , t , J = 7 . 2 Hz ) , 6 . 99 ( 8 H , m ) , 5 . 10 ( 2 H , s ) , 3 . 77 ( 3 H , s ) .