1 H NMR ( 700 . 03 MHz , DMSO - d 6 ) δ 1 . 79 - 1 . 81 ( 2 H , m ) , 2 . 55 ( 2 H , d ) , 3 . 79 ( 2 H , d ) , 4 . 19 - 4 . 22 ( 2 H , m ) , 4 . 63 ( 2 H , s ) , 6 . 67 ( 2 H , d ) , 6 . 71 ( 1 H , t ) , 7 . 07 - 7 . 09 ( 2 H , m ) , 7 . 66 ( 1 H , d ) , 8 . 29 ( 1 H , d ) , 8 . 81 ( 1 H , s ) ; m / z = 418 [ M + H ] +.