morphine  levo  class : phenanthrene     

beznoquinone (metabolite of morphine) toxic less active than morphine 

3-deoxymorphine  lower analgesic effect than morphine (less potent)  more lipophilic (more CNS)  less affinity to receptor  high bioavia  

codiene  methoxy on c3 (usally anti tussive)  less potent than morphine (less analgesic activity) more lipophilic increased CNS penetration