1 H - NMR ( 300 MHz , CDCl 3 ) δ 1 . 23 ( d , 6 H ) , 1 . 77 - 1 . 94 ( m , 4 H ) , 2 . 62 ( m , 2 H ) , 2 . 65 ( m , 1 H ) , 2 . 76 ( m , 1 H ) , 2 . 79 ( s , 3 H ) , 3 . 38 ( m , 2 H ) , 3 . 83 ( brd , 2 H ) , 4 . 32 ( t , 2 H ) , 4 . 40 ( t , 2 H ) , 6 . 74 ( d , 1 H ) , 7 . 17 ( dd , 1 H ) , 7 . 51 ( s , 1 H ) , 7 . 86 ( d , 1 H ) , 9 . 34 ( s , 1 H , NH ) ; MS ( m / e , M +): 382