1 H NMR ( 500 . 133 MHz , DMSO - d 6 ) δ 2 . 43 - 2 . 48 ( 4 H , m ) , 3 . 36 ( 2 H , s ) , 3 . 54 - 3 . 60 ( 4 H , m ) , 5 . 96 ( 1 H , s ) , 6 . 63 ( 1 H , s ) , 6 . 65 - 6 . 68 ( 1 H , m ) , 7 . 56 ( 1 H , d ) , 8 . 21 ( 1 H , d ) , 10 . 57 ( 1 H , s ) ; m / z = 352 [ M + H ] +.