Simple and Efficient Synthesis of -Succinimidyl-4-[F]fluorobenzoate ([F]SFB)-An Important Intermediate for the Introduction of Fluorine-18 into Complex Bioactive Compounds.

-succinimidyl-[F]fluorobenzoate ([F]SFB) is commonly prepared through a three-step procedure starting from [F]fluoride ion. A number of methods for the single-step radiosynthesis of [F]SFB have been introduced recently, including the radiofluorination of diaryliodonium salts and the Cu-mediated F-fluorination of pinacol aryl boronates and aryl tributyl stannanes, but they still have the drawbacks of lengthy product purification procedures. In the present work, two approaches for the direct labeling of [F]SFB from diaryliodonium (DAI) salt () and pinacol aryl boronate () are evaluated, with a major focus on developing a fast and simple SPE-based purification procedure.

Automation of Copper-Mediated F-Fluorination of Aryl Pinacol Boronates Using 4-Dimethylaminopyridinium Triflate.

Currently, the copper-mediated radiofluorination of aryl pinacol boronates (arylBPin) using the commercially available, air-stable Cu(OTf)2Py4 catalyst is one of the most efficient synthesis approaches, greatly facilitating access to a range of radiotracers, including drug-like molecules with nonactivated aryl scaffolds. Further adjustment of this methodology, in particular, the [F]fluoride recovery step for the routine preparation of radiotracers, has been the focus of recent research. In our recent study, an organic solution of 4-dimethylaminopyridinium trifluoromethanesulfonate (DMAPOTf) was found to be an efficient PTC for eluting radionuclides retained on the weak anion exchange cartridge, Oasis WAX 1cc, employing the inverse sorption-elution protocol.

One-Pot Radiosynthesis of [F]Anle138b-5-(3-Bromophenyl)-3-(6-[F]fluorobenzo[][1,3]dioxol-5-yl)-1-pyrazole-A Potential PET Radiotracer Targeting α-Synuclein Aggregates.

Availability of PET imaging radiotracers targeting α-synuclein aggregates is important for early diagnosis of Parkinson's disease and related α-synucleinopathies, as well as for the development of new therapeutics. Derived from a pyrazole backbone, C-labelled derivatives of anle138b (3-(1,3-benzodioxol-5-yl)-5-(3-bromophenyl)-1-pyrazole)-an inhibitor of α-synuclein and prion protein oligomerization-are currently in active development as the candidates for PET imaging α-syn aggregates. This work outlines the synthesis of a radiotracer based on the original structure of anle138b, labelled with fluorine-18 isotope, eminently suitable for PET imaging due to half-life and decay energy characteristics (97% β+ decay, 109.

Automated Optimized Synthesis of [F]FLT Using Non-Basic Phase-Transfer Catalyst with Reduced Precursor Amount.

3′-deoxy-3′-[18F]fluorothymidine ([18F]FLT) is a positron emission tomography (PET) tracer useful for tumor proliferation assessment for a number of cancers, particularly in the cases of brain, lung, and breast tumors. At present [18F], FLT is commonly prepared by means of the nucleophilic radiofluorination of 3-N-Boc-5′-O-DMT-3′-O-nosyl thymidine precursor in the presence of a phase-transfer catalyst, followed by an acidic hydrolysis. To achieve high radiochemical yield, relatively large amounts of precursor (20−40 mg) are commonly used, leading to difficulties during purification steps, especially if a solid-phase extraction (SPE) approach is attempted.

Production of 6-l-[F]Fluoro--tyrosine in an Automated Synthesis Module for C-Labeling.

6-l-[F]Fluoro--tyrosine (6-l-[F]FMT) represents a valuable alternative to 6-l-[F]FDOPA which is conventionally used for the diagnosis and staging of Parkinson's disease. However, clinical applications of 6-l-[F]FMT have been limited by the paucity of practical production methods for its automated production. Herein we describe the practical preparation of 6-l-[F]FMT using alcohol-enhanced Cu-mediated radiofluorination of Bpin-substituted chiral Ni(II) complex in the presence of non-basic BuONTf using a volatile PrOH/MeCN mixture as reaction solvent.

Rapid F-labeling via Pd-catalyzed S-arylation in aqueous medium.

We report radiolabeling of thiol-containing substrates via Pd-catalyzed S-arylation with 2-[F]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.

Nucleophilic Synthesis of 6-l-[F]FDOPA. Is Copper-Mediated Radiofluorination the Answer?

Positron emission tomography employing 6-l-[F]fluoro-3,4-dihydroxyphenylalanine (6-l-[F]FDOPA) is currently a highly relevant clinical tool for detection of gliomas, neuroendocrine tumors and evaluation of Parkinson's disease progression. Yet, the deficiencies of electrophilic synthesis of 6-l-[F]FDOPA hold back its wider use. To fulfill growing clinical demands for this radiotracer, novel synthetic strategies via direct nucleophilic F-radiloabeling starting from multi-Curie amounts of [F]fluoride, have been recently introduced.

Alcohol-Supported Cu-Mediated F-Fluorination of Iodonium Salts under "Minimalist" Conditions.

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 GMP production of imaging probes in automated synthesis modules.

Synthesis and biological evaluation of 2-(3,4-dimethoxyphenyl)-6-(2-[F]fluoroethoxy)benzothiazole ([F]FEDBT) for PET imaging of breast cancer.

Given the ever-present demand for improved PET radiotracer in oncology imaging, we have synthesized 2-(3,4-dimethoxyphenyl)-6-(2-[F]fluoroethoxy)benzothiazole ([F]FEDBT), a fluorine-18-containing fluoroethylated benzothiazole to explore its utility as a PET imaging tracer. [F]FEDBT was prepared via kryptofix-mediated nucleophilic substitution of the tosyl group precursor. Fractionated ethanol-based solid-phase (SPE cartridge-based) purification afforded [F]FEDBT in 60% radiochemical yield (EOB), with radiochemical purity in excess of 98% and the specific activity was 35GBq/μmol.

4-[18F]fluoroglutamic acid (BAY 85-8050), a new amino acid radiotracer for PET imaging of tumors: synthesis and in vitro characterization.

There is a high demand for tumor specific PET tracers in oncology imaging. Besides glucose, certain amino acids also serve as energy sources and anabolic precursors for tumors. Therefore, (18)F-labeled amino acids are interesting probes for tumor specific PET imaging.

[18F]flumazenil binding to central benzodiazepine receptor studies by PET--quantitative analysis and comparisons with [11C]flumazenil.

[(11)C]flumazenil is the reference radioligand for Positron Emission Tomography (PET) studies of central benzodiazepine (BZ) receptors. Fluorine is available in the flumazenil molecule and [(18)F]flumazenil has recently been prepared. The aim of the present PET-study in 8 male subjects was to examine the binding of [(18)F]flumazenil in the human brain by direct comparison with [(11)C]flumazenil.

A fully automated one-pot synthesis of [carbonyl-11C]WAY-100635 for clinical PET applications.

A fully automated synthesis of the important 5HT(1A) receptor radioligand, [carbonyl-(11)C]WAY-100635 (I), was developed based on the optimized one-pot "wet" synthesis procedure. A modern automated apparatus was constructed from commercially available components and operated via LabView software. In average, (906+/-525)MBq (n=94) of (I) was obtained from 40 min bombardment at 50 microA beam current within 50 min synthesis time.

No carrier added synthesis of O-(2'-[18F]fluoroethyl)-L-tyrosine via a novel type of chiral enantiomerically pure precursor, NiII complex of a (S)-tyrosine Schiff base.

O-(2'-[(18)F]fluoroethyl)-l-tyrosine ([(18)F]FET) has gained much attention as a promising amino acid radiotracer for tumor imaging with positron emission tomography (PET) due to favorable imaging characteristics and relatively long half-life of (18)F (110min) allowing remote-site application. Here we present a novel type of chiral enantiomerically pure labeling precursor for [(18)F]FET, based on NiII complex of a Schiff's base of (S)-[N-2-(N'-benzylprolyl)amino]benzophenone (BPB) with alkylated (S)-tyrosine, Ni-(S)-BPB-(S)-Tyr-OCH2CH2X (X=OTs (3a), OMs (3b) and OTf (3c)). A series of compounds 3a-c was synthesized in three steps from commercially available reagents.

Preparation of highly specific radioactivity [18F]flumazenil and its evaluation in cynomolgus monkey by positron emission tomography.

A straightforward method for the preparation of no-carrier-added (n.c.a.