Exploring transition metal fluoride chelates – synthesis, properties and prospects towards potential PET probes

Abstract

A series of 1st row transition metal trifluoride complexes with neutral N3-donor ligands is described; radiolabelling of [FeF3(BnMe2-tacn); in aqueous MeCN is achieved by 18F/19F isotopic exchange and its stability in PBS and serum established.

Late-Stage 18F/19F Isotopic Exchange for the Synthesis of 18F-Labeled Sulfamoyl Fluorides

“…Although high molar activity is only necessary to image low-density targets, such as neuroreceptors, there have been several new drug candidates that do not stringently require high molar activity during the initial assessments of their pharmacological properties. In addition, 18 F/ 19 F isotopic exchange has proven to be useful in various applications, as shown in Figure a, and can be a valuable alternative to yield 18 F-labeled PET radiopharmaceuticals or radiotracers, especially when considering that other approaches to introduce 18 F are ineffective. Moreover, this approach relieves the synthetic burden of separate preparation of labeling precursors and avoids the extra screening process required for judicious radiolabeling methods.…”

Isotope Exchange-Based 18F-Labeling Methods

“…Blower et al showed similar results (Scheme b) that [FeF 3 (BnMe 2 -tacn)] ( 128 ) can be obtained by coordinating tacn derivatives with FeF 3 , which not only exhibited good stability but also requires only 24 nM of precursor amount to achieve the corresponding radiofluorination (Table ).…”

18F‐Labeling Chemistry in Aqueous Media

“…Aqueous 18 F-labeling via FeÀ 18 F bond formation More recently, Reid's group continued to evaluate possible applications of d 3 -transition metal (Cr(III), Mn(III), Fe(III), and Co(III)) trifluoro compounds in the development of PET tracers (Scheme 26). [107] They reported the first example of direct 18 Ffluorination of transition metal Fe through the formation of three fluorine substitutions FeÀ 18 F bonds in one step via isotope exchange by using the same ligand as that used for GaF 3 to form a chelate-like complex. The reaction was conducted at 80 °C using 2.4 nmol of the precursor in CH 3 CN/H 2 O (v/v = 75/ 25), and ~13 % RCY was obtained.…”