2-[¹⁸F]Fluoroethyl tosylate - a versatile tool for building ¹⁸F-based radiotracers for positron emission tomography

Positron emission tomography (PET) is a modern in vivo imaging technique and an important diagnostic modality for clinical and pre-clinical research. The incorporation of a radionuclide like fluorine-18 into a target molecule to form PET radiopharmaceuticals is a repeated challenge for radiochemists. ¹⁸F-Fluoroethylation is a well acknowledged method for ¹⁸F-radiolabeling and 2-[ ¹⁸F]fluoroethyltosylate ([ ¹⁸ F]FEts) is a preferred reagent because of its high reactivity to phenolic, thiophenolic, carboxylic and amide functions. The review will highlight the role of [ ¹⁸F]FEts in PET-chemistry, and summarize its applicability in radiotracer design. The radiolabeling conditions and pros and cons of direct and indirect radiolabeling as well the aspects of reactivity of [ ¹⁸F]FEts compared with other [ ¹⁸F]fluoroalkylating reagents will be discussed comprehensively.