1 H NMR ( 399 . 9 MHz , DMSO - d 6 ) δ 1 . 44 ( 9 H , s ) , 1 . 71 - 1 . 72 ( 2 H , m ) , 1 . 88 - 1 . 90 ( 2 H , m ) , 3 . 13 ( 2 H , d ) , 3 . 97 ( 2 H , d ) , 4 . 29 ( 2 H , s ) , 7 . 54 ( 1 H , d ) , 8 . 28 ( 1 H , d ) ; m / z = 399 [ M + H ] +.