1 H NMR ( 399 . 9 MHz , DMSO - d 6 ) δ 1 . 40 ( 9 H , s ) , 1 . 71 ( 4 H , m ) , 2 . 67 ( 3 H , s ) , 3 . 05 ( 2 H , m ) , 4 . 06 ( 1 H , s ) , 4 . 38 ( 2 H , m ) , 7 . 63 ( 1 H , d ) , 8 . 24 ( 1 H , d ) ; m / z = 401 [ M + H ] +.