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Hoffmann C, Kolks N, Smets D, Haseloer A, Gröner B, Urusova EA, Endepols H, Neumaier F, Ruschewitz U, Klein A, Neumaier B, Zlatopolskiy BD. Next Generation Copper Mediators for the Efficient Production of 18 F-Labeled Aromatics. Chemistry 2023; 29:e202202965. [PMID: 36214204 PMCID: PMC10100267 DOI: 10.1002/chem.202202965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Indexed: 11/07/2022]
Abstract
Cu-mediated radiofluorination is a versatile tool for the preparation of 18 F-labeled (hetero)aromatics. In this work, we systematically evaluated a series of complexes and identified several generally applicable mediators for highly efficient radiofluorination of aryl boronic and stannyl substrates. Utilization of these mediators in nBuOH/DMI or DMI significantly improved 18 F-labeling yields despite use of lower precursor amounts. Impressively, application of 2.5 μmol aryl boronic acids was sufficient to achieve 18 F-labeling yields of up to 75 %. The practicality of the novel mediators was demonstrated by efficient production of five PET-tracers and transfer of the method to an automated radiosynthesis module. In addition, (S)-3-[18 F]FPhe and 6-[18 F]FDOPA were prepared in activity yields of 23±1 % and 30±3 % using only 2.5 μmol of the corresponding boronic acid or trimethylstannyl precursor.
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Affiliation(s)
- Chris Hoffmann
- Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany.,Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
| | - Niklas Kolks
- Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany.,Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
| | - Daniel Smets
- Faculty of Mathematics and Natural Sciences, Department of Chemistry, Institute of Inorganic Chemistry, University of Cologne, Greinstr. 6, 50939, Cologne, Germany
| | - Alexander Haseloer
- Faculty of Mathematics and Natural Sciences, Department of Chemistry, Institute of Inorganic Chemistry, University of Cologne, Greinstr. 6, 50939, Cologne, Germany
| | - Benedikt Gröner
- Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany.,Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
| | - Elizaveta A Urusova
- Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany.,Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
| | - Heike Endepols
- Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany.,Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany.,Faculty of Medicine and University Hospital Cologne, Department of Nuclear Medicine, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany
| | - Felix Neumaier
- Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany.,Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
| | - Uwe Ruschewitz
- Faculty of Mathematics and Natural Sciences, Department of Chemistry, Institute of Inorganic Chemistry, University of Cologne, Greinstr. 6, 50939, Cologne, Germany
| | - Axel Klein
- Faculty of Mathematics and Natural Sciences, Department of Chemistry, Institute of Inorganic Chemistry, University of Cologne, Greinstr. 6, 50939, Cologne, Germany
| | - Bernd Neumaier
- Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany.,Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
| | - Boris D Zlatopolskiy
- Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany.,Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
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Cressy D, Akula M, Frederick A, Shipley K, Osborne D. A method for the nucleophilic fluorination of 4-dimethylaminopyridine (DMAP) pyridinium salts. RESULTS IN CHEMISTRY 2023. [DOI: 10.1016/j.rechem.2022.100706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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3
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Reissig F, Mamat C. Strained Ammonium Precursors for Radiofluorinations. ChemistryOpen 2022; 11:e202200039. [PMID: 35736542 PMCID: PMC9220932 DOI: 10.1002/open.202200039] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 05/24/2022] [Indexed: 12/11/2022] Open
Abstract
The increasing application of positron emission tomography (PET) in nuclear medicine has stimulated the extensive development of a multitude of novel and versatile techniques to introduce fluorine-18, especially for the radiolabelling of biologically or pharmacologically active molecules. Taking into consideration that the introduction of fluorine-18 (t1/2 =109.8 min) mostly proceeds under harsh conditions, radiolabelling of such molecules represents a challenge and is of enormous interest. Ideally, it should proceed in a regioselective manner under mild physiological conditions, in an acceptable time span, with high yields and high specific activities. Special attention has been drawn to 2-fluoroethyl and 3-fluoropropyl groups, which are often the active sites of radiofluorinated compounds. Precursors containing an ammonium leaving group - such as a strained azetidinium or aziridinium moiety - can help to overcome these obstacles leading to a convenient and mild introduction of [18 F]fluoride with high radiochemical yields.
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Affiliation(s)
- Falco Reissig
- Institut für Radiopharmazeutische Krebsforschung Helmholtz-Zentrum Dresden-RossendorfBautzner Landstraße 40001328DresdenGermany
- Fakultät Chemie und LebensmittelchemieTechnische Universität Dresden01062DresdenGermany
| | - Constantin Mamat
- Institut für Radiopharmazeutische Krebsforschung Helmholtz-Zentrum Dresden-RossendorfBautzner Landstraße 40001328DresdenGermany
- Fakultät Chemie und LebensmittelchemieTechnische Universität Dresden01062DresdenGermany
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Bailey JJ, Wuest M, Wagner M, Bhardwaj A, Wängler C, Wängler B, Valliant JF, Schirrmacher R, Wuest F. Synthesis and Preclinical Evaluation of [ 18F]SiFA-PSMA Inhibitors in a Prostate Cancer Model. J Med Chem 2021; 64:15671-15689. [PMID: 34672630 DOI: 10.1021/acs.jmedchem.1c00812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Positron emission tomography (PET) imaging of prostate-specific membrane antigen (PSMA) with gallium-68 (68Ga) and fluorine-18 (18F) radiotracers has aroused tremendous interest over the past few years. The use of organosilicon-[18F]fluoride acceptors (SiFA) conjugated to urea-based peptidomimetic PSMA inhibitors provides a "kit-like" multidose synthesis technology. Nine novel 18F-labeled SiFA-bearing PSMA inhibitors with different linker moieties were synthesized and analyzed for their in vitro binding against [125I]I-TAAG-PSMA in LNCaP cells. IC50 values ranged from 58-570 nM. Among all compounds, [18F]SiFA-Asp2-PEG3-PSMA (IC50 = 125 nM) showed the highest tumor uptake in LNCaP tumors (SUV60min 0.73). A substantial increase in molar activity (Am) (from 7.5 ± 0.5 to 86 ± 3 GBq/μmol) led to a significant increase in LNCaP tumor uptake (SUV60min 1.18; Δ 0.45 corresponding to +62%). In vivo blocking with DCFPyL resulted in -32% uptake after 60 min. The SiFA-isotopic exchange chemistry offers a method that is readily adaptable for a "kit-type" labeling procedure and clinical translation.
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Affiliation(s)
- Justin J Bailey
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada
| | - Melinda Wuest
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada
| | - Michael Wagner
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada
| | - Atul Bhardwaj
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada
| | - Carmen Wängler
- Clinic of Radiology and Nuclear Medicine, Biomedical Chemistry and Clinic of Radiology and Nuclear Medicine, Molecular Imaging and Radiochemistry, Medical Faculty Mannheim of Heidelberg University, Theodor-Kutzer-Ufer 1-3, Mannheim 68167, Germany
| | - Bjoern Wängler
- Clinic of Radiology and Nuclear Medicine, Biomedical Chemistry and Clinic of Radiology and Nuclear Medicine, Molecular Imaging and Radiochemistry, Medical Faculty Mannheim of Heidelberg University, Theodor-Kutzer-Ufer 1-3, Mannheim 68167, Germany
| | - John F Valliant
- Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street, Hamilton, Ontario L8S 4K1, Canada
| | - Ralf Schirrmacher
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada
| | - Frank Wuest
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada
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Humpert S, Omrane MA, Urusova EA, Gremer L, Willbold D, Endepols H, Krasikova RN, Neumaier B, Zlatopolskiy BD. Rapid 18F-labeling via Pd-catalyzed S-arylation in aqueous medium. Chem Commun (Camb) 2021; 57:3547-3550. [PMID: 33870341 DOI: 10.1039/d1cc00745a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We report radiolabeling of thiol-containing substrates via Pd-catalyzed S-arylation with 2-[18F]fluoro-5-iodopyridine, which is readily accessible using the "minimalist" radiofluorination method. The practicality of the procedure was confirmed by preparation of a novel PSMA-specific PET-tracer as well as labeling of glutathione, Aβ oligomer-binding RD2 peptide, bovine serum albumin and PSMA I&S.
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Affiliation(s)
- Swen Humpert
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Jülich 52428, Germany.
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Mamat C. Editorial for the special Issue "Jörg Steinbach". J Labelled Comp Radiopharm 2020; 62:350-351. [PMID: 31141614 DOI: 10.1002/jlcr.3773] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 05/20/2019] [Indexed: 12/14/2022]
Abstract
This special issue of Journal of Labelled Compounds and Radiopharmaceuticals is dedicated to commemorate the outstanding scientific work of Jörg Steinbach, former director of the Institute of Radiopharmaceutical Cancer Research at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and full professor for Bioinorganic and Radiopharmaceutical Chemistry at the Technical University Dresden. Current legal regulations brought to an end the formal attachment of Professor Steinbach to the TU Dresden as well as the directorship of the institute within his 65th birthday. A festive symposium has been held at the HZDR on the occasion of his retirement on September 5th, 2018, one day after the inauguration of the new Centre for Radiopharmaceutical Tumor Research at the HZDR.
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Affiliation(s)
- Constantin Mamat
- Institut für Radiopharmazeutische Krebsforschung, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
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Richard M, Specklin S, Roche M, Hinnen F, Kuhnast B. Original synthesis of radiolabeling precursors for batch and on resin one-step/late-stage radiofluorination of peptides. Chem Commun (Camb) 2020; 56:2507-2510. [PMID: 32003763 DOI: 10.1039/c9cc09434b] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Radiolabeling of peptides with fluorine-18 is hurdled by their chemical sensitivity and complicated processes. Original triflyl-pyridine intermediates afforded ammonium precursors that were radiolabeled at low temperature. From that study, a generic tag has been designed to allow a simple one-step/late-stage radiolabelling of peptides. The strategy has been transposed to an automated "on-resin" radiolabelling.
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Affiliation(s)
- Mylène Richard
- Université Paris Saclay, CEA, INSERM, CNRS, BioMaps, Service Hospitalier Frédéric Joliot, Bertrand KUHNAST, 4 place du général Leclerc, 91401 Orsay, France.
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One-step 18F-fluorination of smart positron emission tomography tracer for sensing furin activity in tumors. Nucl Med Biol 2020; 82-83:72-79. [PMID: 32109829 DOI: 10.1016/j.nucmedbio.2020.02.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 01/13/2020] [Accepted: 02/18/2020] [Indexed: 12/15/2022]
Abstract
INTRODUCTION Peptide analogues have attracted considerable attention in the field of developing novel positron emission tomography (PET) imaging agents due to their unique properties. Nevertheless, the complicated radiolabeling process and fast metabolism usually pose challenges to the clinical applications of peptide-based molecular probes. Herein a novel PET tracer containing a specific peptide sequence Arg-Val-Arg-Arg (RVRR), Acetyl-Arg-Val-Arg-Arg-Cys(StBu)-Gly(AMB[18F]F3)-CBT ([18F]1), was designed and radiosynthesized using a simple and convenient one-step 18F-fluorination procedure. The smart tracer can be activated by the protease furin and then undergoes an intermolecular cyclization reaction in tumor cells, leading to improved PET imaging efficiency of tumor. METHODS The radiosynthesis of the target tracer [18F]1 and the control tracer [18F]1-ctrl was performed under facile conditions in pyridazine-HCl buffer (pH~2.5) at 80 °C within 30 min. The enzyme-controlled condensation was studied for non-radioactive compound 1 in the human breast cancer cell lysates (MDA-MB-468). The cellular uptake of [18F]1 and [18F]1-ctrl was studied and compared by measuring the activity in MDA-MB-468 cells using a γ-counter after incubation with 37 kBq of [18F]1 or [18F]1-ctrl, respectively. In vivo behavior of [18F]1 was examined through PET imaging of MDA-MB-468 tumor-bearing mice and compared with that of [18F]1-ctrl as well as that of [18F]1 co-injected with non-radioactive compound 1. RESULTS The tracer [18F]1 was obtained with a high radiochemical yield (RCY) of 42.5 ± 1.47% and an excellent radiochemical purity (RCP > 99%). Under the activation of furin and GSH, the tracer suffered a condensation reaction to form dimers and then self-assembled into nanoparticles to produce enduring signal. The cellular uptake of [18F]1 and [18F]1-ctrl was determined to be 10.2 ± 0.37 and 1.19 ± 0.25%ID at 120 min, respectively. For in vivo PET imaging, [18F]1 exhibited the optimum tumor uptake of 2.39 ± 0.31%ID/g and the tumor-to-muscle uptake ratio of 2.93 ± 0.92 at 10 min post injection. Co-injection of [18F]1 and non-radioactive compound 1 produced a high tumor uptake ranging from 2.83 ± 0.23%ID/g to 3.40 ± 0.18%ID/g at 10 min and 60 min post injection, respectively. CONCLUSIONS The one-step labeling method of tracer [18F]1 showed advantage in simplifying the radiolabeling process with high RCY, which could enable a real kit process for the synthesis of 18F-radiopharmaceuticals and was significant for the large-scale production of tracers for clinical applications. PET imaging results suggested that the tracer [18F]1 had good tumor uptake and the co-injection strategy of [18F]1 with 1 could enhance the imaging signal in tumor.
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The chemistry of labeling heterocycles with carbon-11 or fluorine-18 for biomedical imaging. ADVANCES IN HETEROCYCLIC CHEMISTRY 2020. [DOI: 10.1016/bs.aihch.2019.11.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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S. Clemente G, Zarganes-Tzitzikas T, Dömling A, H. Elsinga P. Late-Stage Copper-Catalyzed Radiofluorination of an Arylboronic Ester Derivative of Atorvastatin. Molecules 2019; 24:E4210. [PMID: 31756986 PMCID: PMC6930542 DOI: 10.3390/molecules24234210] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 11/07/2019] [Accepted: 11/18/2019] [Indexed: 02/06/2023] Open
Abstract
There is an unmet need for late-stage 18F-fluorination strategies to label molecules with a wide range of relevant functionalities to medicinal chemistry, in particular (hetero)arenes, aiming to obtain unique in vivo information on the pharmacokinetics/pharmacodynamics (PK/PD) using positron emission tomography (PET). In the last few years, Cu-mediated oxidative radiofluorination of arylboronic esters/acids arose and has been successful in small molecules containing relatively simple (hetero)aromatic groups. However, this technique is sparsely used in the radiosynthesis of clinically significant molecules containing more complex backbones with several aromatic motifs. In this work, we add a new entry to this very limited database by presenting our recent results on the 18F-fluorination of an arylboronic ester derivative of atorvastatin. The moderate average conversion of [18F]F- (12%), in line with what has been reported for similarly complex molecules, stressed an overview through the literature to understand the radiolabeling variables and limitations preventing consistently higher yields. Nevertheless, the current disparity of procedures reported still hampers a consensual and conclusive output.
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Affiliation(s)
- Gonçalo S. Clemente
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, The Netherlands
| | - Tryfon Zarganes-Tzitzikas
- Department of Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Alexander Dömling
- Department of Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Philip H. Elsinga
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, The Netherlands
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Orlovskaya VV, Modemann DJ, Kuznetsova OF, Fedorova OS, Urusova EA, Kolks N, Neumaier B, Krasikova RN, Zlatopolskiy BD. Alcohol-Supported Cu-Mediated 18F-Fluorination of Iodonium Salts under "Minimalist" Conditions. Molecules 2019; 24:molecules24173197. [PMID: 31484375 PMCID: PMC6749259 DOI: 10.3390/molecules24173197] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 08/29/2019] [Accepted: 09/02/2019] [Indexed: 02/01/2023] Open
Abstract
In the era of personalized precision medicine, positron emission tomography (PET) and related hybrid methods like PET/CT and PET/MRI gain recognition as indispensable tools of clinical diagnostics. A broader implementation of these imaging modalities in clinical routine is closely dependent on the increased availability of established and emerging PET-tracers, which in turn could be accessible by the development of simple, reliable, and efficient radiolabeling procedures. A further requirement is a cGMP production of imaging probes in automated synthesis modules. Herein, a novel protocol for the efficient preparation of 18F-labeled aromatics via Cu-mediated radiofluorination of (aryl)(mesityl)iodonium salts without the need of evaporation steps is described. Labeled aromatics were prepared in high radiochemical yields simply by heating of iodonium [18F]fluorides with the Cu-mediator in methanolic DMF. The iodonium [18F]fluorides were prepared by direct elution of 18F- from an anion exchange resin with solutions of the corresponding precursors in MeOH/DMF. The practicality of the novel method was confirmed by the racemization-free production of radiolabeled fluorophenylalanines, including hitherto unknown 3-[18F]FPhe, in 22-69% isolated radiochemical yields as well as its direct implementation into a remote-controlled synthesis unit.
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Affiliation(s)
| | - Daniel J Modemann
- Institute of Neuroscience and Medicine, INM-5: Nuclear Chemistry, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
| | - Olga F Kuznetsova
- N.P.Bechtereva Institute of the Human Brain, 197376 St.-Petersburg, Russia.
| | - Olga S Fedorova
- N.P.Bechtereva Institute of the Human Brain, 197376 St.-Petersburg, Russia.
| | - Elizaveta A Urusova
- Institute of Neuroscience and Medicine, INM-5: Nuclear Chemistry, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
- Institute of Radiochemistry and Experimental Molecular Imaging, University Clinic Cologne, 50937 Cologne, Germany.
| | - Niklas Kolks
- Institute of Neuroscience and Medicine, INM-5: Nuclear Chemistry, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
- Institute of Radiochemistry and Experimental Molecular Imaging, University Clinic Cologne, 50937 Cologne, Germany.
| | - Bernd Neumaier
- Institute of Neuroscience and Medicine, INM-5: Nuclear Chemistry, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
- Institute of Radiochemistry and Experimental Molecular Imaging, University Clinic Cologne, 50937 Cologne, Germany.
- Max Planck Institute for Metabolism Research, 50931 Cologne, Germany.
| | - Raisa N Krasikova
- N.P.Bechtereva Institute of the Human Brain, 197376 St.-Petersburg, Russia.
- St.-Petersburg State University, 199034 St.-Petersburg, Russia.
| | - Boris D Zlatopolskiy
- Institute of Neuroscience and Medicine, INM-5: Nuclear Chemistry, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
- Institute of Radiochemistry and Experimental Molecular Imaging, University Clinic Cologne, 50937 Cologne, Germany.
- Max Planck Institute for Metabolism Research, 50931 Cologne, Germany.
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