1 H - NMR ( 300 MHz , CDCl 3 ) δ 1 . 90 - 2 . 03 ( m , 4 H ) , 2 . 21 ( s , 3 H ) , 2 . 39 ( m , 1 H ) , 2 . 43 ( m , 2 H ) , 2 . 80 ( s , 3 H ) , 2 . 82 ( m , 2 H ) , 3 . 07 ( m , 2 H ) , 3 . 58 ( m , 2 H ) , 4 . 40 ( t , 2 H ) , 6 . 93 ( d , 1 H ) , 7 . 20 ( dd , 1 H ) , 7 . 42 ( brs , 1 H , NH ) , 7 . 58 ( d , 1 H ) , 8 . 48 ( s , 1 H , NH ) ; MS ( m / e , M +): 354