Synthesis of an affinity ligand ('UPHIT') for in vivo acylation of the kappa-opioid receptor.
The isothiocyanate analog (1S,2S-trans-2-isothiocyanato-4,5-dichloro-N- methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide, 3a) of the highly selective kappa-opioid receptor agonist, U50,488, was prepared as a potential site-directed affinity ligand for acylation of kappa-opioid receptors in vivo. The isothiocyanate (3a) which we have designated UPHIT and its enantiomer (3b) were synthesized in 3 steps starting from optically pure (1S,2S)-(+)-trans-2-pyrrolidinyl-N-methyl-cyclohexylamine (4a) and its enantiomer (4b), respectively, thus defining their absolute stereochemistry. Binding in vitro of the 1S,2S enantiomer 3a to kappa receptors labelled by [3H]U69,593 was shown to occur with an IC50 value of 25.92 +/- 0.36 nM, whereas 827.42 +/- 5.88 and 115.10 +/- 1.23 nM were obtained for the IC50 value of the 1R,2R enantiomer (3b) and (+/-)-3 respectively. Intracerebroventricular (ICV) injection of 100 micrograms of (+/-)-3 into guinea-pig brain followed by analysis of remaining kappa-binding sites 24 h later revealed that (+/-)-3 depleted 98% of the kappa receptors that bind [3H]U69,593 and 40% of those that bind [3H]bremazocine. These preliminary data suggest exciting uses for these compounds in furthering our knowledge of the kappa-opioid receptor.
de Costa
B R
BR
Laboratory of Medicinal Chemistry, National Institute of Digestive, Diabetes, and Kidney Diseases, Bethesda, MD 20892.
Band
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L
Rothman
R B
RB
Jacobson
A E
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Bykov
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Pert
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Rice
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KC
D000215:Acylation; D000345:Affinity Labels / Q000138:chemical synthesis*; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D006168:Guinea Pigs; D008297:Male; D011957:Receptors, Opioid / Q000378:metabolism*; D017473:Receptors, Opioid, kappa
D000345:Affinity Labels; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa