1 H - NMR ( 400 MHz , DMSO - d 6 ) δ : 7 . 87 ( 2 H , d , J = 8 . 8 Hz ) , 7 . 71 ( 2 H , d , J = 8 . 8 Hz ) , 7 . 36 ( 2 H , d , J = 8 . 4 Hz ) , 7 . 19 ( 1 H , d , J = 8 . 0 Hz ) , 6 . 98 ( 2 H , d , J = 8 . 4 Hz ) , 6 . 80 ( 1 H , s ) , 6 . 66 ( 1 H , dd , J = 6 . 0 and 2 . 0 Hz ) , 5 . 09 ( 1 H , s ) , 3 . 77 ( 1 H , s ) , 2 . 80 ( 4 H , t , J = 7 . 2 Hz ) , 2 . 00 ( 2 H , q , J = 7 . 2 Hz ) .