Use of SF6 for the production of electrophilic 18F-fluorination reagents

Electrophilic F-18-fluorination is an important method for production of tracers for positron emission tomography. The most commonly employed F-18-fluorination reagents [F-18]F-2, [F-18]Selectfluor bis(triflate) and [F-18] NFSi allow for the synthetically simple and fast introduction of fluorine-18 into organic molecules, in particular those containing electron rich aromatic rings. For the time being the best method for the production of [F-18]F2 gas, the most common electrophilic reagent, is a post-target production which applies a high voltage electrical discharge to promote the F-18/F-18 isotopic exchange between [F-18]MeF and carrier F-2 gas.The aim of this study was to develop a new method for the production of electrophilic F-18-fluorination reagents which would avoid use of toxic and very reactive carrier F-2 gas. In this study the use of SF6 as an alternative to carrier F-2 gas was tested. Experiments were carried out in two different matrix gases: Ne and Xe. The electrophilic F-18-fluorination reagent produced was used for the labelling of two model compounds (6-[F-18] fluoro-L-DOPA and [F-18]Selectfluor bis(triflate)) in order to prove its feasibility.This proof-of-concept study showed that SF6 in Xe can be used in place of F-2 for the production of electrophilic [F-18]F-2 gas. When SF6 in Ne was used only trace amounts of [F-18]F-2 was observed.