Octahydro-1,2,3,4,4a,5,11,11a-pyrido[3,4-c][1,5]benzoxazepines: conformationally restricted fentanyl analogs

Synthesis, analgesic activity and preliminary molecular modeling studies of the cis- and trans-fused octahydro-1,2,3,4,4a,5,11,11a-pyrido[3,4-c][1,5]benzoxazepines8 and 9, the first rigid fentanyl analogs with a conformationally restricted 4-anilido group that retain antinociceptive properties, are reported.