Conformationally restrained fentanyl analogs. 2. Synthesis and analgetic evaluation of perhydro-1,6-naphthyridin-2-ones

Abstract
Conformational flexibility of the N-acyl portion of fentanyl-type analgetics was restricted through the synthesis of novel perhydro-1,6-naphthyridin-2-one derivatives. Neither the cis-fused derivative, the trans-fused derivative nor the enamide possessed analgetic activity in the mouse tail-flick assay, reaffirming the sensitivity of this portion of 4-anilidopiperidine analgetics to conformational restraint.