Probes for narcotic receptor mediated phenomena. 44. Synthesis of an N-substituted 4-hydroxy-5-(3-hydroxyphenyl)morphan with high affinity and selective mu-antagonist activity.

Article Details

Citation

Copy to clipboard

Iyer MR, Lee YS, Deschamps JR, Dersch CM, Rothman RB, Jacobson AE, Rice KC

Probes for narcotic receptor mediated phenomena. 44. Synthesis of an N-substituted 4-hydroxy-5-(3-hydroxyphenyl)morphan with high affinity and selective mu-antagonist activity.

Eur J Med Chem. 2012 Apr;50:44-54. doi: 10.1016/j.ejmech.2012.01.025. Epub 2012 Jan 20.

PubMed ID

22341895 [ View in PubMed

]

Abstract

A simple three-step synthesis of 5-(3-hydroxyphenyl)-2-methyl-2-azabicyclo[3.3.1]nonan-4-ol (3a) was achieved using an osmium tetroxide mediated oxidation of the known intermediate 6. A pyrrolidine-ring variant of 3a (3-(7-(hydroxymethyl)-6-methyl-6-azabicyclo[3.2.1]octan-1-yl)phenol (5)) was isolated when other routes were used. The epimeric hydroxy analogue 4a was synthesized by simple inversion of the stereochemistry at C-4. Both N-methyl (3a and 4a) and N-phenethyl (3b and 4b) derivatives were synthesized. The compounds were examined for their opioid receptor affinity and the N-phenethyl analogue 3b was found to have relatively weak affinity for the mu-opioid receptor (K(i) = 74 nM). However, the N-phenethyl analogue of the C-4 epimer, 4b, had about 15 fold higher affinity than 3b and was selective for the mu-opioid receptor (K(i) = 4.6 nM). Compound 4b was a moderately potent mu-opioid antagonist (K(e) = 12 nM), as determined by [(35)S]GTP-gamma-S assays. Compounds 3b and 4b were energy minimized at the level of B3LYP/6-31G*, and then overlaid onto the 5-phenylmorphan, the (1R,5R,9S)-(-)-enantiomer of 2b (Fig. 1) with the alpha or beta-OH group at the C-9 position. The spatial orientation of the hydroxyl moiety in 3b, 4b, 2a, and 2b is proposed to be the structural requirement for high mu-opioid receptor binding affinity and their agonist or antagonist activity. The modest change in spatial position of the hydroxyl moiety, and not the N-substituent, induced the change from potent agonist to an antagonist of moderate potency.

DrugBank Data that Cites this Article

Binding Properties

Drug	Target	Property	Measurement	pH	Temperature (°C)
Morphine	Kappa-type opioid receptor	Ki (nM)	299	N/A	N/A	Details
Morphine	Mu-type opioid receptor	Ki (nM)	2.6	N/A	N/A	Details