1 H NMR ( 399 . 9 MHz , DMSO - d 6 ) δ 1 . 86 - 1 . 89 ( 2 H , m ) , 2 . 15 ( 2 H , td ) , 3 . 44 - 3 . 51 ( 2 H , m ) , 4 . 16 - 4 . 19 ( 2 H , m ) , 6 . 28 ( 1 H , s ) , 7 . 62 ( 1 H , d ) , 7 . 66 ( 1 H , d ) , 7 . 72 ( 1 H , d ) , 8 . 26 ( 1 H , d ) ; m / z = 371 [ M + H ] +.