Abstract: A method of treating pain or pruritis comprising administering to a patient in need thereof a pharmaceutically effective amount of a ? opioid receptor agonist of the formula wherein R is an alkyl having an amino group as a substituent; and R1 is acyl.

Abstract: A compound or a salt thereof having the following formula wherein R1 is acyl, R2 is hydrogen, halogen, unsubstituted alkyl or alkyl substituted by halogen; R3 is halogen or alkoxy; R4 is cycloalkyl, unsubstituted alkyl or alkyl substituted by cycloalkyl, aryl or hydroxyl or an ester thereof or alkoxy; R5 is hydroxyl or an ester thereof, alkoxy or alkoxyalkyl; or R4 and R5 are bonded with each other to form a pyrrolidine ring substituted by hydroxyl or an ester thereof, alkoxy or alkoxyalkyl; R6 is hydroxyl or an ester thereof, alkoxy, alkoxyalkoxy, alkoxyalkoxyalkoxy, mercapto or alkylthio; and A1 and A2, are the same or different, and are alkylene, provided that (i) when R4 and R5 are bonded to each other to form the pyrrolidine ring substituted by hydroxyl or an ester thereof, R2 is halogen; (ii) when R4 and R5 are bonded to each other to form the pyrrolidine ring substituted by alkoxyalkyl, R2 is hydrogen; (iii) when R6 is hydroxyl or an ester thereof, R4 is isopropyl.

Abstract: A method of treating pain or pruritis comprising administering to a patient in need thereof a pharmaceutically effective amount of a ? opioid receptor agonist of the formula wherein R is an alkyl having an amino group as a substituent; and R1 is acyl.