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Bertoli G, Martínez ÁM, Goebel JF, Belmonte D, Sivendran N, Gooßen LJ. C-H Fluoromethoxylation of Arenes by Photoredox Catalysis. Angew Chem Int Ed Engl 2023; 62:e202215920. [PMID: 36385731 PMCID: PMC10107189 DOI: 10.1002/anie.202215920] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 11/15/2022] [Accepted: 11/16/2022] [Indexed: 11/18/2022]
Abstract
Redox-active N-(fluoromethoxy)benzotriazoles were made accessible from fluoroacetic acid and hydroxybenzotriazoles via electrodecarboxylative coupling. After alkylation, they become effective monofluoromethoxylation reagents, enabling the photocatalytic C-H functionalization of arenes. Thus, irradiation of 1-(OCH2 F)-3-Me-6-(CF3 )benzotriazolium triflate with blue LED light in the presence of [Ru(bpy)3 (PF6 )2 ] promotes the synthesis of diversely functionalized aryl monofluoromethyl ethers. This method allows the late-stage functionalization of biologically relevant structures without relying on ecologically problematic halofluorocarbons.
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Affiliation(s)
- Giulia Bertoli
- Fakultät für Chemie und BiochemieRuhr-Universität BochumUniversitätsstraße 15044801BochumGermany
| | - Ángel Manu Martínez
- Fakultät für Chemie und BiochemieRuhr-Universität BochumUniversitätsstraße 15044801BochumGermany
| | - Jonas F. Goebel
- Fakultät für Chemie und BiochemieRuhr-Universität BochumUniversitätsstraße 15044801BochumGermany
| | - Debora Belmonte
- Fakultät für Chemie und BiochemieRuhr-Universität BochumUniversitätsstraße 15044801BochumGermany
| | - Nardana Sivendran
- Fakultät für Chemie und BiochemieRuhr-Universität BochumUniversitätsstraße 15044801BochumGermany
| | - Lukas J. Gooßen
- Fakultät für Chemie und BiochemieRuhr-Universität BochumUniversitätsstraße 15044801BochumGermany
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Sun J, Xiao Z, Haider A, Gebhard C, Xu H, Luo HB, Zhang HT, Josephson L, Wang L, Liang SH. Advances in Cyclic Nucleotide Phosphodiesterase-Targeted PET Imaging and Drug Discovery. J Med Chem 2021; 64:7083-7109. [PMID: 34042442 DOI: 10.1021/acs.jmedchem.1c00115] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cyclic nucleotide phosphodiesterases (PDEs) control the intracellular concentrations of cAMP and cGMP in virtually all mammalian cells. Accordingly, the PDE family regulates a myriad of physiological functions, including cell proliferation, differentiation and apoptosis, gene expression, central nervous system function, and muscle contraction. Along this line, dysfunction of PDEs has been implicated in neurodegenerative disorders, coronary artery diseases, chronic obstructive pulmonary disease, and cancer development. To date, 11 PDE families have been identified; however, their distinct roles in the various pathologies are largely unexplored and subject to contemporary research efforts. Indeed, there is growing interest for the development of isoform-selective PDE inhibitors as potential therapeutic agents. Similarly, the evolving knowledge on the various PDE isoforms has channeled the identification of new PET probes, allowing isoform-selective imaging. This review highlights recent advances in PDE-targeted PET tracer development, thereby focusing on efforts to assess disease-related PDE pathophysiology and to support isoform-selective drug discovery.
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Affiliation(s)
- Jiyun Sun
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States
| | - Zhiwei Xiao
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States
| | - Achi Haider
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States
| | - Catherine Gebhard
- Department of Nuclear Medicine, University Hospital Zurich, Raemistrasse 100, Zurich 8006, Switzerland
- Center for Molecular Cardiology, University of Zurich, Wagistrasse 12, Schlieren 8952, Switzerland
| | - Hao Xu
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, 613 West Huangpu Road, Tianhe District, Guangzhou 510630, China
| | - Hai-Bin Luo
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Han-Ting Zhang
- Departments of Neuroscience, Behavioral Medicine & Psychiatry, and Physiology & Pharmacology, the Rockefeller Neuroscience Institute, West Virginia University Health Sciences Center, Morgantown, West Virginia 26506, United States
| | - Lee Josephson
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States
| | - Lu Wang
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, 613 West Huangpu Road, Tianhe District, Guangzhou 510630, China
| | - Steven H Liang
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States
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Moghadam ES, Tehrani MH, Csuk R, Fischer L, Faramarzi MA, Rashidi A, Javadi I, Amini M. 2,4-Disubstituted Quinazoline Derivatives Act as Inducers of Tubulin Polymerization: Synthesis and Cytotoxicity. Anticancer Agents Med Chem 2020; 19:1048-1057. [PMID: 30868963 DOI: 10.2174/1871520619666190314125254] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 03/04/2019] [Accepted: 03/05/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND During last recent years number of anti-tubulin agents were introduced for treatment of diverse kind of cancer. Despite of their potential in treatment of cancer, drug resistance and adverse toxicity such as peripheral neuropathy are some of the negative criteria of anti-tubulin agents. METHODS Twenty seven quinazoline derivatives were synthesized using a multicomponent reaction. The cytotoxicity of compounds 1-27 was tested in SRB assays employing five different human tumor cell lines. Effect of two of active compounds on tubulin polymerization was also checked using a commercially available assay kit. Molecular modelling studies were also performed using autodock tools software. RESULTS SRB assays showed that compounds 2, 9, 16 and 26, being highly cytotoxic with IC50 values ranging between 2.1 and 14.3µM. The possible mode of action of compounds, 2, 9, 16 and 26, and the taxol binding site of the protein tubulin, an important goal for antimitotic drugs, was also studied by molecular docking, which showed reasonable interactions with tubulin active site, followed by investigation of the effects of compounds 9 and 16 on the polymerization of tubulin. The results showed the tested compounds to be highly active as inducers of tubulin polymerization. CONCLUSION Altogether, with respect to obtained results, it is attractive and beneficial to further investigation on quinazoline scaffold as antimitotic agents.
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Affiliation(s)
- Ebrahim S Moghadam
- Department of Medicinal Chemistry, Faculty of Pharmacy and Drug Design and Development Research Center, The Institute of Pharmaceutical Sciences (TIPS), Tehran University of Medical Sciences, Tehran 1417614411, Iran
| | - Maryam H Tehrani
- Department of Medicinal Chemistry, Faculty of Pharmacy and Drug Design and Development Research Center, The Institute of Pharmaceutical Sciences (TIPS), Tehran University of Medical Sciences, Tehran 1417614411, Iran
| | - René Csuk
- Martin-Luther-University Halle-Wittenberg, Organic Chemistry, Kurt-Mothes-Str. 2, D-06120 Halle (Saale), Germany
| | - Lucie Fischer
- Martin-Luther-University Halle-Wittenberg, Organic Chemistry, Kurt-Mothes-Str. 2, D-06120 Halle (Saale), Germany
| | - Mohammad Ali Faramarzi
- Department of Pharmaceutical Biotechnology, Faculty of Pharmacy and Biotechnology Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Arezoo Rashidi
- Department of Pharmaceutical Biotechnology, Faculty of Pharmacy and Biotechnology Research Center, Tehran University of Medical Sciences, Tehran, Iran.,Department of Toxicology, Faculty of Pharmacy, Shahreza Branch, Islamic Azad University, Shahreza, Iran
| | - Iraj Javadi
- Department of Toxicology, Faculty of Pharmacy, Shahreza Branch, Islamic Azad University, Shahreza, Iran
| | - Mohsen Amini
- Department of Medicinal Chemistry, Faculty of Pharmacy and Drug Design and Development Research Center, The Institute of Pharmaceutical Sciences (TIPS), Tehran University of Medical Sciences, Tehran 1417614411, Iran
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Politanskaya LV, Selivanova GA, Panteleeva EV, Tretyakov EV, Platonov VE, Nikul’shin PV, Vinogradov AS, Zonov YV, Karpov VM, Mezhenkova TV, Vasilyev AV, Koldobskii AB, Shilova OS, Morozova SM, Burgart YV, Shchegolkov EV, Saloutin VI, Sokolov VB, Aksinenko AY, Nenajdenko VG, Moskalik MY, Astakhova VV, Shainyan BA, Tabolin AA, Ioffe SL, Muzalevskiy VM, Balenkova ES, Shastin AV, Tyutyunov AA, Boiko VE, Igumnov SM, Dilman AD, Adonin NY, Bardin VV, Masoud SM, Vorobyeva DV, Osipov SN, Nosova EV, Lipunova GN, Charushin VN, Prima DO, Makarov AG, Zibarev AV, Trofimov BA, Sobenina LN, Belyaeva KV, Sosnovskikh VY, Obydennov DL, Usachev SA. Organofluorine chemistry: promising growth areas and challenges. RUSSIAN CHEMICAL REVIEWS 2019. [DOI: 10.1070/rcr4871] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Alam MM, Hassan AHE, Kwon YH, Lee HJ, Kim NY, Min KH, Lee SY, Kim DH, Lee YS. Design, synthesis and evaluation of alkylphosphocholine-gefitinib conjugates as multitarget anticancer agents. Arch Pharm Res 2017; 41:35-45. [DOI: 10.1007/s12272-017-0977-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 10/19/2017] [Indexed: 01/28/2023]
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Mori W, Takei M, Furutsuka K, Fujinaga M, Kumata K, Muto M, Ohkubo T, Hashimoto H, Tamagnan G, Higuchi M, Kawamura K, Zhang MR. Comparison between [ 18F]fluorination and [ 18F]fluoroethylation reactions for the synthesis of the PDE10A PET radiotracer [ 18F]MNI-659. Nucl Med Biol 2017; 55:12-18. [PMID: 28972915 DOI: 10.1016/j.nucmedbio.2017.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 08/04/2017] [Accepted: 08/15/2017] [Indexed: 12/20/2022]
Abstract
INTRODUCTION 2-(2-(3-(4-(2-[18F]Fluoroethoxy)phenyl)-7-methyl-4-oxo-3,4-dihydroquinazolin-2-yl)ethyl)-4-isopropoxyisoindoline-1,3-dione ([18F]MNI-659, [18F]1) is a useful PET radiotracer for imaging phosphodiesterase 10A (PDE10A) in human brain. [18F]1 has been previously prepared by direct [18F]fluorination of a tosylate precursor 2 with [18F]F-. The aim of this study was to determine the conditions for the [18F]fluorination reaction to obtain [18F]1 of high quality and with sufficient radioactivity for clinical use in our institute. Moreover, we synthesized [18F]1 by [18F]fluoroethylation of a phenol precursor 3 with [18F]fluoroethyl bromide ([18F]FEtBr), and the outcomes of [18F]fluorination and [18F]fluoroethylation were compared. METHODS We performed the automated synthesis of [18F]1 by [18F]fluorination and [18F]fluoroethylation using a multi-purpose synthesizer. We determined the amounts of tosylate precursor 2 and potassium carbonate as well as the reaction temperature for direct [18F]fluorination. RESULTS The efficiency of the [18F]fluorination reaction was strongly affected by the amount of 2 and potassium carbonate. Under the determined reaction conditions, [18F]1 with 0.82±0.2GBq was obtained in 13.6%±3.3% radiochemical yield (n=8, decay-corrected to EOB and based on [18F]F-) at EOS, starting from 11.5±0.4GBq of cyclotron-produced [18F]F-. On the other hand, the [18F]fluoroethylation of 3 with [18F]FEtBr produced [18F]1 with 1.0±0.2GBq and in 22.5±2.5 % radiochemical yields (n=7, decay-corrected to EOB and based on [18F]F-) at EOS, starting from 7.4GBq of cyclotron-produced [18F]F-. Clearly, [18F]fluoroethylation resulted in a higher radiochemical yield of [18F]1 than [18F]fluorination. CONCLUSION [18F]1 of high quality and with sufficient radioactivity was successfully radiosynthesized by two methods. [18F]1 synthesized by direct [18F]fluorination has been approved and will be provided for clinical use in our institute.
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Affiliation(s)
- Wakana Mori
- National Institute of Radiological Science, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Makoto Takei
- National Institute of Radiological Science, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Kenji Furutsuka
- National Institute of Radiological Science, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; SHI Accelerator Service Ltd., Tokyo 141-0032, Japan
| | - Masayuki Fujinaga
- National Institute of Radiological Science, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Katsushi Kumata
- National Institute of Radiological Science, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Masatoshi Muto
- National Institute of Radiological Science, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; Tokyo Nuclear Services Ltd., Tokyo 110-0016, Japan
| | - Takayuki Ohkubo
- National Institute of Radiological Science, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; SHI Accelerator Service Ltd., Tokyo 141-0032, Japan
| | - Hiroki Hashimoto
- National Institute of Radiological Science, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | | | - Makoto Higuchi
- National Institute of Radiological Science, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Kazunori Kawamura
- National Institute of Radiological Science, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Ming-Rong Zhang
- National Institute of Radiological Science, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan.
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Wagner S, Teodoro R, Deuther-Conrad W, Kranz M, Scheunemann M, Fischer S, Wenzel B, Egerland U, Hoefgen N, Steinbach J, Brust P. Radiosynthesis and biological evaluation of the new PDE10A radioligand [ 18 F]AQ28A. J Labelled Comp Radiopharm 2016; 60:36-48. [PMID: 27896836 DOI: 10.1002/jlcr.3471] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 08/19/2016] [Accepted: 10/12/2016] [Indexed: 01/10/2023]
Abstract
Cyclic nucleotide phosphodiesterase 10A (PDE10A) regulates the level of the second messengers cAMP and cGMP in particular in brain regions assumed to be associated with neurodegenerative and psychiatric diseases. A better understanding of the pathophysiological role of the expression of PDE10A could be obtained by quantitative imaging of the enzyme by positron emission tomography (PET). Thus, in this study we developed, radiolabeled, and evaluated a new PDE10A radioligand, 8-bromo-1-(6-[18 F]fluoropyridin-3-yl)-3,4-dimethylimidazo[1,5-a]quinoxaline ([18 F]AQ28A). [18 F]AQ28A was radiolabeled by both nucleophilic bromo-to-fluoro or nitro-to-fluoro exchange using K[18 F]F-K2.2.2 -carbonate complex with different yields. Using the superior nitro precursor, we developed an automated synthesis on a Tracerlab FX F-N module and obtained [18 F]AQ28A with high radiochemical yields (33 ± 6%) and specific activities (96-145 GBq·μmol-1 ) for further evaluation. Initially, we investigated the binding of [18 F]AQ28A to the brain of different species by autoradiography and observed the highest density of binding sites in striatum, the brain region with the highest PDE10A expression. Subsequent dynamic PET studies in mice revealed a region-specific accumulation of [18 F]AQ28A in this region, which could be blocked by preinjection of the selective PDE10A ligand MP-10. In conclusion, the data suggest [18 F]AQ28A is a suitable candidate for imaging of PDE10A in rodent brain by PET.
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Affiliation(s)
- Sally Wagner
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | - Rodrigo Teodoro
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | - Winnie Deuther-Conrad
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | - Mathias Kranz
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | - Matthias Scheunemann
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | - Steffen Fischer
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | - Barbara Wenzel
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | | | | | - Jörg Steinbach
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | - Peter Brust
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Department of Neuroradiopharmaceuticals, Leipzig, Germany
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Cloning and characterization of three ketoreductases from soil metagenome for preparing optically active alcohols. Biotechnol Lett 2016; 38:1799-808. [DOI: 10.1007/s10529-016-2167-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Accepted: 06/21/2016] [Indexed: 10/21/2022]
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Novel Radioligands for Cyclic Nucleotide Phosphodiesterase Imaging with Positron Emission Tomography: An Update on Developments Since 2012. Molecules 2016; 21:molecules21050650. [PMID: 27213312 PMCID: PMC6273803 DOI: 10.3390/molecules21050650] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 05/09/2016] [Accepted: 05/10/2016] [Indexed: 12/19/2022] Open
Abstract
Cyclic nucleotide phosphodiesterases (PDEs) are a class of intracellular enzymes that inactivate the secondary messenger molecules, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Thus, PDEs regulate the signaling cascades mediated by these cyclic nucleotides and affect fundamental intracellular processes. Pharmacological inhibition of PDE activity is a promising strategy for treatment of several diseases. However, the role of the different PDEs in related pathologies is not completely clarified yet. PDE-specific radioligands enable non-invasive visualization and quantification of these enzymes by positron emission tomography (PET) in vivo and provide an important translational tool for elucidation of the relationship between altered expression of PDEs and pathophysiological effects as well as (pre-)clinical evaluation of novel PDE inhibitors developed as therapeutics. Herein we present an overview of novel PDE radioligands for PET published since 2012.
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Development of highly potent phosphodiesterase 10A (PDE10A) inhibitors: Synthesis and in vitro evaluation of 1,8-dipyridinyl- and 1-pyridinyl-substituted imidazo[1,5-a]quinoxalines. Eur J Med Chem 2015; 107:97-108. [PMID: 26562545 DOI: 10.1016/j.ejmech.2015.10.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 10/13/2015] [Accepted: 10/14/2015] [Indexed: 12/12/2022]
Abstract
Herein we report the synthesis of fluorinated inhibitors of phosphodiesterase 10A (PDE10A) which can be used potentially as lead structure for the development of a (18)F-labeled PDE10A imaging agent for positron emission tomography. The use of ortho-fluoropyridines as residues could potentially enable the introduction of (18)F through nucleophilic substitution for radiolabeling purposes. 2-Fluoropyridines are introduced by a Suzuki coupling at different positions of the molecule. The reference compounds, 1,8-dipyridinylimidazo[1,5-a]quinoxalines and 1-pyridinylimidazo[1,5-a]quinoxalines, show inhibitory potencies at best in the subnanomolar range and selectivity factors greater than 38 against other PDE's. 1,8-Dipyridinylimidazo[1,5-a]quinoxalines are more potent inhibitors than 1-pyridinylimidazo[1,5-a]quinoxalines. Using 2-fluoro-3-pyridinyl as residue provided the most potent inhibitors 16 (IC50 = 0.12 nM), 17 (IC50 = 0.048 nM) and 32 (IC50 = 0.037 nM).
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