1 H NMR ( 399 . 9 MHz , DMSO - d 6 ) δ 2 . 56 - 2 . 61 ( 4 H , m ) , 3 . 64 ( 4 H , t ) , 3 . 66 ( 2 H , s ) , 7 . 53 - 7 . 54 ( 1 H , m ) , 7 . 55 - 7 . 56 ( 1 H , m ) , 7 . 60 ( 1 H , d ) , 7 . 77 ( 1 H , t ) , 8 . 26 ( 1 H , d ) ; m / z = 444 [ M + H ] +.