1 H NMR ( 300 . 132 MHz , DMSO - d 6 ) δ 2 . 58 - 2 . 67 ( 4 H , m ) , 3 . 59 - 3 . 68 ( 4 H , m ) , 3 . 76 ( 2 H , s ) , 6 . 82 ( 1 H , s ) , 7 . 18 - 7 . 32 ( 2 H , m ) , 7 . 52 - 7 . 63 ( 3 H , m ) , 8 . 24 ( 1 H , d ) ; m / z = 403 [ M + H ] +.