1 H - NMR ( 400 MHz , DMSO - d 6 ) δ : 7 . 77 - 7 . 74 ( 2 H , m ) , 7 . 52 - 7 . 32 ( 9 H , m ) , 6 . 98 ( 3 H , t , J = 9 . 9 Hz ) , 6 . 90 ( 2 H , d , J = 9 . 0 Hz ) , 5 . 21 ( 2 H , s ) , 5 . 07 ( 2 H , s ) , 4 . 70 ( 2 H , t , J = 8 . 8 Hz ) , 3 . 25 ( 2 H , t , J = 9 . 0 Hz ) .