Morphinan cyclic imines and pyrrolidines containing a constrained phenyl group: High affinity opioid agonists

A series of morphinan derivatives which are cyclic imines and pyrrolidines containing a constrained phenyl group has been synthesised and tested for their opioid receptor binding affinity. In opioid binding assays the ligands displayed very high affinity particularly for μ receptors and some showed substantial μ selectivity.