Accelerated gas-liquid visible light photoredox catalysis with continuous-flow photochemical microreactors

In this protocol, we describe the construction and use of an operationally simple photochemical microreactor for gas-liquid photoredox catalysis using visible light. The general procedure includes details on how to set up the microreactor appropriately with inlets for gaseous reagents and organic starting materials, and it includes examples of how to use it to achieve continuous-flow preparation of disulfides or trifluoromethylated heterocycles and thiols. The reported photomicroreactors are modular, inexpensive and can be prepared rapidly from commercially available parts within 1 h even by nonspecialists. Interestingly, typical reaction times of gas-liquid visible light photocatalytic reactions performed in microflow are lower (in the minute range) than comparable reactions performed as a batch process (in the hour range). This can be attributed to the improved irradiation efficiency of the reaction mixture and the enhanced gas-liquid mass transfer in the segmented gas-liquid flow regime

multi‐patient dose synthesis of [18F]Flumazenil via a copper‐mediated 18F‐fluorination

Background Flumazenil (FMZ) is a functionally silent imidazobenzodiazepine which binds to the benzodiazepine binding site of approximately 75% of the brain γ-aminobutyric acid-A receptors (GABAARs). Positron Emission Tomography (PET) imaging of the GABAARs with [11C]FMZ has been used to evidence alterations in neuronal density, to assess target engagement of novel pharmacological agents, and to study disorders such as epilepsy and Huntington’s disease. Despite the potential of FMZ PET imaging the short half-life (t1/2) of carbon-11 (20 min) has limited the more widespread clinical use of [11C]FMZ. The fluorine-18 (18F) isotopologue with a longer t1/2 (110 min) is ideally suited to address this drawback. However, the majority of current radiochemical methods for the synthesis of [18F]FMZ are non-trivial and low yielding. We report a robust, automated protocol that is good manufacturing practice (GMP) compatible, and yields multi-patient doses of [18F]FMZ. Results The fully automated synthesis was developed on the Trasis AllinOne (AIO) platform using a single-use cassette. [18F]FMZ was synthesized in a one-step procedure from [18F]fluoride, via a copper-mediated 18F-fluorination of a boronate ester precursor. Purification was performed by semi-preparative radio-HPLC and the collected fraction formulated directly into the final product vial. The overall process from start of synthesis to delivery of product is approximately 55 min. Starting with an initial activity of 23.6 ± 5.8 GBq (n = 3) activity yields of [18F]FMZ were 8.0 ± 1 GBq (n = 3). The synthesis was successfully reproduced at two independent sites, where the product passed quality control release criteria in line with the European Pharmacopoeia standards and ICH Q3D(R1) guidelines to be suitable for human use. Conclusion Reported is a fully automated cassette-based synthesis of [18F]FMZ that is Good Manufacturing Practice (GMP) compatible and produces multi-patient doses of [18F]FMZ

[18F]Difluorocarbene for Positron Emission Tomography

The advent of total-body Positron Emission Tomography (PET) has vastly broadened the range of research and clinical applications of this powerful molecular imaging technology1. Such possibilities have accelerated progress in 18F-radiochemistry with numerous methods available to 18F-label (hetero)arenes and alkanes2. However, access to 18F-difluoromethylated molecules in high molar activity (Am) is largely an unsolved problem, despite the indispensability of the difluoromethyl group for pharmaceutical drug discovery3. We report herein a general solution by introducing carbene chemistry to the field of nuclear imaging with a [18F]difluorocarbene reagent capable of a myriad of 18F-difluoromethylation processes. In contrast to the tens of known difluorocarbene reagents, this 18F-reagent is carefully designed for facile accessibility, high molar activity and versatility. The issue of Am is solved using an assay examining the likelihood of isotopic dilution upon variation of the electronics of the difluorocarbene precursor. Versatility is demonstrated with multiple [18F]difluorocarbene based reactions including O–H, S–H and N–H insertions, and cross-couplings that harness the reactivity of ubiquitous functional groups such as (thio)phenols, N-heteroarenes, and aryl boronic acids that are easy to install. Impact is illustrated with the labelling of highly complex and functionalised biologically relevant molecules and radiotracers

Multi-patient dose synthesis of [18F]Flumazenil via a copper-mediated 18F-fluorination.

peer reviewed("[en] BACKGROUND: Flumazenil (FMZ) is a functionally silent imidazobenzodiazepine which binds to the benzodiazepine binding site of approximately 75% of the brain γ-aminobutyric acid-A receptors (GABAARs). Positron Emission Tomography (PET) imaging of the GABAARs with [11C]FMZ has been used to evidence alterations in neuronal density, to assess target engagement of novel pharmacological agents, and to study disorders such as epilepsy and Huntington's disease. Despite the potential of FMZ PET imaging the short half-life (t1/2) of carbon-11 (20 min) has limited the more widespread clinical use of [11C]FMZ. The fluorine-18 (18F) isotopologue with a longer t1/2 (110 min) is ideally suited to address this drawback. However, the majority of current radiochemical methods for the synthesis of [18F]FMZ are non-trivial and low yielding. We report a robust, automated protocol that is good manufacturing practice (GMP) compatible, and yields multi-patient doses of [18F]FMZ. RESULTS: The fully automated synthesis was developed on the Trasis AllinOne (AIO) platform using a single-use cassette. [18F]FMZ was synthesized in a one-step procedure from [18F]fluoride, via a copper-mediated 18F-fluorination of a boronate ester precursor. Purification was performed by semi-preparative radio-HPLC and the collected fraction formulated directly into the final product vial. The overall process from start of synthesis to delivery of product is approximately 55 min. Starting with an initial activity of 23.6 ± 5.8 GBq (n = 3) activity yields of [18F]FMZ were 8.0 ± 1 GBq (n = 3). The synthesis was successfully reproduced at two independent sites, where the product passed quality control release criteria in line with the European Pharmacopoeia standards and ICH Q3D(R1) guidelines to be suitable for human use. CONCLUSION: Reported is a fully automated cassette-based synthesis of [18F]FMZ that is Good Manufacturing Practice (GMP) compatible and produces multi-patient doses of [18F]FMZ.","[en] ",""