Opiate-like peptides. Part IV. Kyotorphin and its analogues: synthesis and analgesic activity.

L-Tyrosyl-L-arginine ( kyotorphin ) and its 8 analogues were synthesized using EEDQ method. Analgesic activity and neurotoxic effect of all dipeptides were examined. Three of analogues investigated display weak analgesic activity occurring on the administration of doses which exert neurotoxic effect. For three other analogues the neurotoxic effect precedes the possible analgesic effect. The remaining two analogues were biologically inactive.