Fluorine-18 Labelling of Small Molecules: The Use of ¹⁸F-Labelled Aryl Fluorides Derived from No-Carrier-Added [¹⁸F]Fluoride as Labelling Precursors

The favourable long-half life, the ease of production and the low enery of the emitted positron make ¹⁸F an ideal radionuclide for PET imaging. Radiochemistry of ¹⁸F basically relies of two distinctive types of reactions: nucleophilic and electrophilic reactions. All syntheses of ¹⁸F-labelled radiotracers are based on either [¹⁸F]fluoride ion or [¹⁸F]fluorine gas as simple the primary labelling precursors which are obtained directly from the cyclotron. They can be applied either directly to the radiosynthesis or they can be transformed into more complex labelling precursors enabling the multi-step built up of organic tracer molecules. The topic of this review is a survey on the application of several ¹⁸F-labelled aryl fluorides as building blocks derived from no-carrier-added (n.c.a.) [¹⁸F]fluoride to built up small mono-molecular PET radiotracers at high specific radioactivity by multi-step synthesis procedures.