1 H NMR ( 399 . 9 MHz , DMSO - d 6 ) δ 3 . 11 ( 4 H , m ) , 3 . 74 ( 4 H , m ) , 6 . 69 ( 2 H , d ) , 6 . 87 ( 2 H , d ) , 7 . 43 - 7 . 69 ( 2 H , m ) , 8 . 22 ( 1 H , d ) , 8 . 87 ( 1 H , s ) ; m / z = 347 [ M + H ] +.