1 H NMR ( 399 . 9 MHz , CDCl 3 ) δ 1 . 51 ( 9 H , s ) , 2 . 55 - 2 . 58 ( 2 H , m ) , 3 . 67 - 3 . 70 ( 2 H , m ) , 3 . 95 ( 3 H , s ) , 4 . 14 - 4 . 18 ( 2 H , m ) , 6 . 23 ( 1 H , m ) , 7 . 22 ( 1 H , d ) , 7 . 38 ( 1 H , d ) , 7 . 93 ( 1 H , dd ) , 8 . 42 ( 1 H , s ) , 8 . 63 ( 1 H , s ) ; m / z = 355 [ M - H ] -.