Evaluation of 2-azabicyclo[2.2..2]octane analogs of 4-anilidopiperidine analgesics.

Eight analogs of the fentanyl-type analgesics, in which the piperidine ring is restricted into a boat conformation, were evaluated for analgesic activity. All analogs were less active than fentanyl, but interesting conformational and structural relationships were observed. Results of the study are discussed.