1 H NMR ( 399 . 9 MHz , DMSO - d 6 ) δ 1 . 56 - 1 . 59 ( 2 H , m ) , 1 . 86 - 1 . 93 ( 2 H , m ) , 2 . 77 - 2 . 80 ( 2 H , m ) , 2 . 92 - 2 . 98 ( 2 H , m ) , 5 . 27 ( 1 H , s ) , 8 . 17 ( 1 H , s ) , 8 . 85 ( 1 H , s ) , 8 . 98 ( 1 H , s ) ; m / z = 247 [ M + H ] +.