1 H NMR ( 499 . 8 MHz , DMSO - d 6 ) δ 2 . 53 ( 4 H , t ) , 3 . 19 ( 4 H , t ) , 3 . 49 ( 2 H , s ) , 3 . 76 ( 3 H , s ) , 6 . 88 - 6 . 92 ( 2 H , m ) , 7 . 25 ( 2 H , d ) , 7 . 53 ( 1 H , s ) , 7 . 71 - 7 . 73 ( 1 H , m ) , 7 . 92 ( 1 H , d ) ; m / z = 392 [ M + H ] +.