1 H NMR ( 499 . 8 MHz , DMSO - d 6 ) δ 2 . 56 ( 4 H , t ) , 3 . 64 ( 4 H , t ) , 3 . 71 ( 2 H , s ) , 7 . 60 ( 1 H , d ) , 7 . 65 ( 2 H , d ) , 8 . 23 ( 2 H , d ) , 8 . 26 ( 1 H , d ) ; m / z = 408 [ M + H ] +.