Design and synthesis of 10-oxo derivative of N-cyclopropylmethyl (−)-6β-acetylthiodihydro-normorphine, a potentially κ-selective opioid receptor ligand

The design and synthesis of 10-oxo derivative of N-cyclopropylmethyl-(−)-6β-acetylthio dihydronormorphine (4) are described. The result of pharmacological assays indicate that compound 4 acts as a μ-opioid receptor antagonist and κ-opioid receptor agonist which is suggested to be more potent analgesic action than that of 1 and morphine through an activation of κ-opioid receptors.