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Arylphenylpyrrolidinylmethylphenoxybenzamides were found to have high affinity and selectivity for κ opioid receptors. On the basis of receptor binding assays in Chinese hamster ovary (CHO) cells expressing cloned human opioid receptors, (S)-3-fluoro-4-(4-((2-(3-fluorophenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide (25) had a K(i) = 0.565 nM for κ opioid receptor binding while having a K(i) = 35.8 nM for μ opioid receptors and a K(i) = 211 nM for δ opioid receptor binding. Compound 25 was also a potent antagonist of κ opioid receptors when tested in vitro using a [(35)S]-guanosine 5'O-[3-thiotriphosphate] ([(35)S]GTP-γ-S) functional assay in CHO cells expressing cloned human opioid receptors. Compounds were also evaluated for potential use as receptor occupancy tracers. Tracer evaluation was done in vivo, using liquid chromatography-tandem mass spectrometry (LC/MS/MS) methods, precluding the need for radiolabeling. (S)-3-Chloro-4-(4-((2-(pyridine-3-yl)pyrrolidin-1-yl)methyl)phenoxy)benzamide (18) was found to have favorable properties for a tracer for receptor occupancy, including good specific versus nonspecific binding and good brain uptake.

Upon reaction with IPy2BF4, 4-substituted anilines give regioselectively the corresponding o-iodoanilines in nearly quantitative yield, in a process that can be carried out on a multigram scale. Palladium-catalyzed coupling of the resulting 2-iodoanilines with (trimethylsilyl)acetylene (TMSA), followed by efficient CuI-mediated nitrogen cyclization onto alkynes with concurrent elimination of the TMS substituent, allows a straightforward elaboration of 5-mono- and 5,7-disubstituted indoles from aromatic amines. This new approach to the aforementioned indoles does not requires protective groups on nitrogen at any step and can be adapted for preparing related 7-monosubstituted indoles. Moreover, examples iterating the process are given, allowing bisannulation and sequential double annulation and resulting in synthesis of benzodipyrroles. Additionally, suitable conditions for iodination of some of the target indoles with IPy2BF4 are discussed.

As part of our ongoing research to identify novel agents acting at metabotropic glutamate 2 (mGlu2) and 3 (mGlu3) receptors, we have previously reported the identification of the C4α-methyl analog of mGlu2/3 receptor agonist 1 (LY354740). This molecule, 1S,2S,4R,5R,6S-2-amino-4-methylbicyclo[3.1.0]hexane-2,6-dicarboxylate 2 (LY541850), exhibited an unexpected mGlu2 agonist/mGlu3 antagonist pharmacological profile, whereas the C4β-methyl diastereomer (3) possessed dual mGlu2/3 receptor agonist activity. We have now further explored this structure-activity relationship through the preparation of cyclic and acyclic C4-disubstituted analogs of 1, leading to the identification of C4-spirocyclopropane 5 (LY2934747), a novel, potent, and systemically bioavailable mGlu2/3 receptor agonist which exhibits both antipsychotic and analgesic properties in vivo. In addition, through the combined use of protein-ligand X-ray crystallography employing recombinant human mGlu2/3 receptor amino terminal domains, molecular modeling, and site-directed mutagenesis, a molecular basis for the observed pharmacological profile of compound 2 is proposed.

Positron emission tomography (PET) coupled to an effective radioligand could provide an important tool for understanding possible links between neuropsychiatric disorders and brain NOP (nociceptin/orphanin FQ peptide) receptors. We sought to develop such a PET radioligand. Highaffinity NOP ligands were synthesized based on a 3-(2'-fluoro-4',5'-dihydrospiro[piperidine-4,7'-thieno[2,3-c]pyran]-1-yl)-2(2-halobenzyl)-N-alkylpropanamide scaffold and from experimental screens in rats, with ex vivo LC-MS/MS measures, three ligands were identified for labeling with carbon-11 and evaluation with PET in monkey. Each ligand was labeled by 11 C-methylation of an N-desmethyl precursor and studied in monkey under baseline and NOP receptor-preblock conditions. The three radioligands, [ 11 C](S)-10a-c, gave similar results. Baseline scans showed high entry of radioactivity into brain to give a distribution reflecting that expected for NOP receptors. Pre-block experiments showed high early peak levels of brain radioactivity which rapidly declined to a much lower level than seen in baseline scans, thereby indicating a high level of receptor-specific binding in baseline experiments. Overall, [ 11 C](S)-10c showed the most favorable receptor-specific signal and kinetics and is now selected for evaluation in human subjects.

The asymmetric synthesis and biological activity of (2S,1'S,2'S,3'R)-2-(2'-carboxy-3'-methylcyclopropyl) glycine 7 and its epimer at the C3' center 6 are described. Compound 7 is a highly potent and selective agonist for group 2 metabotropric glutamate receptors (mGluRs). It is also systemically 4 orders of magnitude more active in the fear-potentiated startle model of anxiety in rats than the rigid constrained bicyclic system LY354740. Therefore, we have shown that high molecular complexity of conformationally constrained bicyclic systems is not a requirement to achieve highly selective and potent group 2 mGluRs agonists.

Our laboratory developed (S)-3-(2′-fluoro-6′,7′-dihydrospiro [piperidine-4,4′-thieno[3,2-c]pyran]-1-yl)-2-(2-fluorobenzyl)-N-methylpropanamide (11C-NOP-1A), a new radioligand for the nociceptin/orphanin FQ peptide (NOP) receptor, with high affinity (Ki, 0.15 nM) and appropriate lipophilicity (measured logD, 3.4) for PET brain imaging. Here, we assessed the utility of 11C-NOP-1A for quantifying NOP receptors in the monkey brain and estimated the radiation safety profile of this radioligand based on its biodistribution in monkeys. Methods Baseline and blocking PET scans were acquired from head to thigh for 3 rhesus monkeys for approximately 120 min after 11C-NOP-1A injection. These 6 PET scans were used to quantify NOP receptors in the brain and to estimate radiation exposure to organs of the body. In the blocked scans, a selective nonradioactive NOP receptor antagonist (SB-612111; 1 mg/kg intravenously) was administered before 11C-NOP-1A. In all scans, arterial blood was sampled to measure the parent radioligand 11C-NOP-1A. Distribution volume (VT; a measure of receptor density) was calculated with a compartment model using brain and arterial plasma data. Radiation-absorbed doses were calculated using the MIRD Committee scheme. Results After 11C-NOP-1A injection, peak uptake of radioactivity in the brain had a high concentration (~5 standardized uptake value), occurred early (~12 min), and thereafter washed out quickly. VT (mL cm−3) was highest in the neocortex (~20) and lowest in hypothalamus and cerebellum (~13). SB-612111 blocked approximately 50%–70% of uptake and reduced VT in all brain regions to approximately 7 mL cm−3. Distribution was well identified within 60 min of injection and stable for the remaining 60 min, consistent with only parent radioligand and not radiometabolites entering the brain. Whole-body scans confirmed that the brain had specific (i.e., displaceable) binding but could not detect specific binding in peripheral organs. The effective dose for humans estimated from the baseline scans in monkeys was 5.0 μSv/MBq. Conclusion 11C-NOP-1A is a useful radioligand for quantifying NOP receptors in the monkey brain, and its radiation dose is similar to that of other 11C-labeled ligands for neuroreceptors. 11C-NOP-1A appears to be a promising candidate for measuring NOP receptors in the human brain.

Background The nociceptin/orphanin-FQ (NOP; or opioid-receptor-like (ORL1)) receptor is localized in the mesolimbic reward pathway and has been suggested to play a role in feeding, mood, stress, and addiction. Since its deorphanization in 1995, there has been a clear dichotomy in the literature regarding whether an agonist or antagonist would provide therapeutic benefit. Specifically, literature reports indicate that NOP receptor antagonists produce efficacy in animal models of hyperphagia and antidepressant-like activity, whereas NOP agonists produce anxiolytic-like effects and dampen reward/addiction behaviors including ethanol consumption. Methods We characterize here the potent, orally-bioavailable NOP antagonist, LY2940094, in rodent models of ethanol consumption, including ethanol self-administration, progressive ratio operant self-administration, stress-induced reinstatement of ethanol-seeking, and in vivo microdialysis in the nucleus accumbens. Results LY2940094 dose-dependently reduced homecage ethanol self-administration in Indiana Alcohol-Preferring (P) and Marchigian Sardinian Alcohol-Preferring (msP) rats, without affecting food/water intake or locomotor activity. Reduced ethanol intake in P rats did not show significant tolerance over 4 days of subchronic dosing. LY2940094 attenuated progressive ratio operant responding and breakpoints for ethanol in P rats. Moreover, stress-induced reinstatement of ethanol-seeking in msP rats was completely blocked by LY2940094. Furthermore, LY2940094 blocked ethanol-stimulated dopamine release in response to ethanol challenge (1.1 g/kg, IP). Conclusions Our findings demonstrate for the first time that blockade of NOP receptors attenuates ethanol self-administration and ethanol-motivated behaviors, stress-induced ethanol-seeking, and ethanol-induced stimulation of brain reward pathways in lines of rats that exhibit excessive ethanol consumption. Results suggest that LY2940094 may have potential therapeutic utility in treating alcohol addiction.