A Resin-Linker-Vector Approach to Radiopharmaceuticals Containing18F: Application in the Synthesis ofO-(2-[18F]-Fluoroethyl)-L-tyrosine

Radiosynthesis and Preclinical Evaluation of m-[18F]FET and [18F]FET-OMe as Novel [18F]FET Analogs for Brain Tumor Imaging

O-([18F]Fluoroethyl)-l-tyrosine ([18F]FET) is actively transported into the brain and cancer cells by LAT1 and possibly other amino acid transporters, which enables brain tumor imaging by positron emission tomography (PET). However, tumor delivery of this probe in the presence of competing amino acids may be limited by a relatively low affinity for LAT1. The aim of the present work was to evaluate the meta-substituted [18F]FET analog m-[18F]FET and the methyl ester [18F]FET-OMe, which were designed to improve tumor delivery by altering the physicochemical, pharmacokinetic, and/or transport properties. Both tracers could be prepared with good radiochemical yields of 41-56% within 66-90 min. Preclinical evaluation with [18F]FET as a reference tracer demonstrated reduced in vitro uptake of [18F]FET-OMe by U87 glioblastoma cells and no advantage for in vivo tumor imaging. In contrast, m-[18F]FET showed significantly improved in vitro uptake and accelerated in vivo tumor accumulation in an orthotopic glioblastoma model. As such, our work identifies m-[18F]FET as a promising alternative to [18F]FET for brain tumor imaging that deserves further evaluation with regard to its transport properties and in vivo biodistribution.

18 F-Fluorination of a supported 2-(aryl-di-tert-butylsilyl)-N-methyl-imidazole for indirect 18 F-labeling of a VH H single-variable domain

Anchoring an imidazole-di-tert-butyl-arylsilane possessing an azido group to a polystyrene resin provided a heterogeneous precursor that was radiolabeled easily using aqueous [18 F]fluoride. After optimizing the conditions (i.e., using DMSO as solvent and heating at 160°C for 15 min), the desired [18 F]fluorosilane was obtained in 24% radiochemical yield (RCY) and 78% radiochemical purity (RCP) using solid-phase extraction as sole purification. Then, this compound was conjugated by strain-promoted alkyne-azide cycloaddition to a model single-variable domain possessing a cyclooctyne tag, yielding to the desired 18 F-labeled bioconjugate in 2% RCY and >95% RCP after purification by a size exclusion chromatography.

Last-step 18F-fluorination of supported 2-(aryl-di-tert-butylsilyl)-N-methyl-imidazole conjugates for applications in positron emission tomography

Aiming for potential applications in positron emission tomography, fully automated productions of ¹⁸F-labelled bioconjugates were achieved using heterogenous precursors obtained by anchoring imidazole-di-tert-butyl-arylsilanes to a polystyrene resin. The reactions were performed using either "batch" or "flow" procedures, avoiding both the time-consuming azeotropic drying and HPLC purifications usually required.

Bioconjugated arylpalladium complexes on solid supports for a convenient last-step synthesis of 11C-labelled tracers for positron emission tomography

Bioconjugated arylpalladium complexes anchored onto polystyrene beads provided [¹¹C]CO-labelled compounds with excellent radiochemical purities after a simple filtration.

Synthesis of [123I]-iodometomidate from a polymer-supported precursor with a large excluded volume

We report on the synthesis of [¹²³I]-iodometomidate from a soluble polymer-supported precursor with a large extent volume. The precursor enabled the synthesis of the [¹²³I]-iodometomidate with high quality without use of HPLC purification.

Solid-supported reagents composed of a copolymer possessing 2-O-sulfonyl mannosides and phase-transfer catalysts for the synthesis of 2-fluoroglucose

We described the synthesis of a solid-supported co-polymer possessing mannosides and phase-transfer catalysts and synthesis of 2-fluoroglucoside from it. We first prepared a soluble copolymer from two allene monomers possessing a precursor for the synthesis of 2-fluoroglycose and a crown ether. The copolymerization of the monomers via the π-ally nickel-catalyst smoothly proceeded at room temperature to provide a desired copolymer without decomposition of the sulfonate esters. The copolymer exhibited high reactivity towards fluorination in comparison with a conventional precursor. We next synthesized the solid-supported copolymer by using the solid-supported initiator attached with TentaGel® resins. TentaGel® enabled polymerization under stirring with stirring bar without decomposition. The solid-supported copolymer exhibited comparable reactivity towards fluorination in comparison with the soluble copolymer. In addition, it can be easily separated from the reaction vessel by filtration.