1 H NMR ( 399 . 9 MHz , DMSO - d 6 ) δ 1 . 14 - 1 . 21 ( 6 H , m ) , 1 . 44 ( 9 H , s ) , 3 . 36 - 3 . 42 ( 2 H , m ) , 3 . 71 ( 1 H , d ) , 3 . 88 ( 1 H , d ) , 4 . 25 - 4 . 35 ( 1 H , m ) , 4 . 47 ( 1 H , s ) , 7 . 59 ( 1 H , d ) , 8 . 28 ( 1 H , d ) ; m / z = 401 [ M + H ] +.