Further synthesis of enkephalinol analogs containing the dipeptide unit Tyr-Arg (kyotorphin).

Abstract
In order to obtain enkephalin derivatives with high analgesic activity, four enkephalinol analogs having the Tyr-D-Arg unit in the N-terminal position were synthesized. Of these, H-Tyr-D-Arg-Gly-MePhe-Met (O)-ol exhibited analgesic activity comparable to that of morphine after intravenous administration to mice.