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Synthesis and Labelling of a Piperazine-Based Library of 11C-Labeled Ligands for Imaging of the Vesicular Acetylcholine Transporter
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
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2014 (English)In: Journal of labelled compounds & radiopharmaceuticals, ISSN 0362-4803, E-ISSN 1099-1344, Vol. 57, no 8, 525-532 p.Article in journal (Refereed) Published
Abstract [en]

The cholinergic system is involved in neurodegenerative diseases, and visualization of cholinergic innervations with positron emission tomography (PET) would be a useful tool in understanding these diseases. A ligand for the vesicular acetylcholine transporter (VAChT), acknowledged as a marker for cholinergic neurons, could serve as such a PET tracer. The aim was to find a VAChT PET tracer using a library concept to create a small but diverse library of labeled compounds. From the same precursor and commercially available aryl iodides 6a-f, six potential VAChT PET tracers, [C-11]-(+/-)5a-f, were C-11-labeled by a palladium (0)-mediated aminocarbonylation, utilizing a standard protocol. The labeled compounds [C-11]-(+/-)5a-f were obtained in radiochemical purities >95% with decay-corrected radiochemical yields and specific radioactivities between 4-25% and 124-597 GBq/mu mol, respectively. Autoradiography studies were then conducted to assess the compounds binding selectivity for VAChT. Labeled compounds [C-11]-(+/-)5d and [C-11]-(+/-)5e showed specific binding but not enough to permit further preclinical studies. To conclude, a general method for a facile synthesis and labeling of a small piperazine-based library of potential PET tracers for imaging of VAChT was shown, and in upcoming work, another scaffold will be explored using this approach.

Place, publisher, year, edition, pages
2014. Vol. 57, no 8, 525-532 p.
Keyword [en]
vesicular acetylcholine transporter, carbonylation, PET, library, C-11-labeling, vesamicol
National Category
Radiology, Nuclear Medicine and Medical Imaging Medicinal Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-231333DOI: 10.1002/jlcr.3208ISI: 000340169500004PubMedID: 24991704OAI: oai:DiVA.org:uu-231333DiVA: diva2:744191
Available from: 2014-09-07 Created: 2014-09-07 Last updated: 2017-10-26
In thesis
1. Exploring Palladium-Mediated 11C/12C-Carbonylation Reactions: PET Tracer Development Targeting the Vesicular Acetylcholine Transporter
Open this publication in new window or tab >>Exploring Palladium-Mediated 11C/12C-Carbonylation Reactions: PET Tracer Development Targeting the Vesicular Acetylcholine Transporter
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The work presented herein describes the utilization and exploration of palladium-mediated incorporations of carbon monoxide and/or [11C]carbon monoxide into compounds and structural motifs with biological relevance.

The first part of the thesis describes the design, synthesis and 11C-labeling of prospective PET tracers for the vesicular acetylcholine transporter (VAChT), a target affected in several neurodegenerative diseases. Different parts of the benzovesamicol scaffold were modified in papers I and II to probe the binding to VAChT. The key motif was an amide functional group, which enabled the use of palladium-mediated 11C/12C-carbonylations to synthesize and evaluate two different sets of structurally related ligands.

The second part of the thesis describes the exploration of different aspects of palladium-mediated 11C/12C-carbonylation reactions. The utilization of unactivated alkyl iodides and bromides as coupling partners in a carbonylative Suzuki-Miyaura reaction was described in paper III. The combination of palladium-catalysis together with visible light irradiation enabled their functionalization via an alkyl radical. The mild conditions, namely the ambient temperature and pressure of carbon monoxide, and the accessible reaction set-up further added to the utility of the method. A palladium(II)-mediated oxidative 11C-carbonylation for synthesis of 11C-labeled ureas was described in paper IV. Utilizing only amines in addition to a palladium-source and [11C]carbon monoxide, the method proved to be facile and robust, thus representing a simplification in relation to methods using other 11C-synthons for synthesis of 11C-labeled ureas. Finally, a palladium(0)-catalyzed carbonylation reaction for synthesis of acylamidines was presented in paper V. The versatility of the method was demonstrated by one-pot cyclizations to form oxadiazoles and triazoles together with the corresponding 11C-carbonylation reaction to produce 11C-labeled acylamidines and an oxadiazole.

The work described herein has thus contributed structural information in the search for a PET tracer for VAChT and identified a viable lead structure for future investigations. Furthermore, investigation of reaction conditions that would allow use of either elusive or accessible substrates led to the development of methods for synthesis and/or 11C-labeling of various carbonylated compounds.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 99 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 241
Keyword
Carbonylation, palladium, carbon-11, radiochemistry, positron emission tomography, vesicular acetylcholine transporter, vesamicol, alkyl halide, oxidative carbonylation, acylamidine, oxadiazole, heterocycle
National Category
Organic Chemistry Other Chemistry Topics
Research subject
Pharmaceutical Science
Identifiers
urn:nbn:se:uu:diva-332359 (URN)978-91-513-0136-5 (ISBN)
Public defence
2017-12-15, Hall B:21, BMC, Husargatan 3, Uppsala, 09:15 (English)
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Supervisors
Available from: 2017-11-24 Created: 2017-10-26 Last updated: 2017-11-24

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Bergman, SaraEstrada, SergioHall, HåkanLarhed, MatsSvedberg, MarieThibblin, AlfAntoni, Gunnar

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