| Abstract
| - We report here the syntheses of N-substituted quinolinimide derivatives displaying sufficient affinity and highselectivity for δ-opioid receptors. Among 9-subsituted derivatives, one showed much higher selectivity for the δreceptor in binding assays than the δ antagonist methylnaltrindole (6: Ki = 42 nM; μ/δ and κ/δ > 238 on ratbrain membranes) and antagonist properties. This compound was labeled with carbon-11 (t1/2 = 20.4 min) as apotential radioligand for the noninvasive assessment of δ opioid receptors in vivo with positron emission tomography(PET). A high yielding radiosynthesis of [11C]-6, based on the [11C]methyl introduction on the pyridine moietyby a Stille reaction, was described (radiochemical yield = 60 ± 10%, specific activities = 0.8 to 1.5 Ci/μmol).The in vivo pharmacological profile in rats indicated that the radiotracer crossed the blood−brain barrier but wasnot stable and underwent rapid degradation in both plasma and brain. No specific binding was consequentlyrevealed.
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