Yuan, Yunyun; Zaidi, Saheem A.; Stevens, David L.; Scoggins, Krista L.; Mosier, Philip D.; Kellogg, Glen E.; Dewey, William L.; Selley, Dana E.; Zhang, Yan
Design, syntheses, and pharmacological characterization of 17-cyclopropylmethyl-3,14 beta-dihydroxy-4,5 alpha-epoxy-6 alpha-(isoquinoline-3 '-carboxamido)morphinan analogues as opioid receptor ligands
BIOORGANIC & MEDICINAL CHEMISTRY, 23:1701-1715, APR 15 2015

A series of 17-cyclopropylmethyl-3,14 beta-dihydroxy-4,5 alpha-epoxy-6 alpha-(isoquinoline-3 '-carboxamido)morphinan (NAQ) analogues were synthesized and pharmacologically characterized to study their structure-activity relationship at the mu opioid receptor (MOR). The competition binding assay showed two-atom spacer and aromatic side chain were optimal for MOR selectivity. Meanwhile, substitutions at the 1 '- and/or 4 '-position of the isoquinoline ring retained or improved MOR selectivity over the kappa opioid receptor while still possessing above 20-fold MOR selectivity over the delta opioid receptor. In contrast, substitutions at the 6 '- and/or 7 '-position of the isoquinoline ring reduced MOR selectivity as well as MOR efficacy. Among this series of ligands, compound 11 acted as an antagonist when challenged with morphine in warm-water tail immersion assay and produced less significant withdrawal symptoms compared to naltrexone in morphine-pelleted mice. Compound 11 also antagonized the intracellular Ca2+ increase induced by DAMGO. Molecular dynamics simulation studies of 11 in three opioid receptors indicated orientation of the 6 '-nitro group varied significantly in the different 'address' domains of the receptors and played a crucial role in the observed binding affinities and selectivity. Collectively, the current findings provide valuable insights for future development of NAQ-based MOR selective ligands. Published by Elsevier Ltd.

DOI:10.1016/j.bmc.2015.02.055

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