Novel nonopioid non-antiinflammatory analgesics: 3-(aminoalkyl)- and 3-[(4-aryl-1-piperazinyl)alkyl]oxazolo[4,5-b]pyridin-2(3H)-ones.

A series of 3-(aminoalkyl)- and 3-[(4-aryl-1-piperazinyl)alkyl]oxazolo[4,5-b]pyridin-2(3H)-ones were prepared from their respective oxazolo[4,5-b]pyridin-2(3H)-ones. Several members of this group were found to possess potent analgesic activity in the mouse during a p-phenylquinone writhing induced test. Among them, phenylpiperazine compounds with two-carbon length alkyl chains, 2a and 2b, appeared by high analgesic with little toxicity having neither an antiinflammatory effect nor opioid receptor affinity. The synthesis and structure-affinity relationships for this series are detailed.