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Cannabinoid receptor 1 (CB1R) controls various physiological and pathological conditions, including memory, motivation, and inflammation, and is thus an interesting target for positron emission tomography (PET). Herein, we report a ruthenium-mediated radiolabeling synthesis and preclinical evaluation of a new CB1R specific radiotracer, [ 18 F]FPATPP. [ 18 F]FPATPP was produced with 16.7 ± 5.7% decay-corrected radiochemical yield and >95 GBq/μmol molar activity. The tracer showed high stability, low defluorination, and high specific binding to CB1Rs in mouse brain.

Background: Copper-mediated radiofluorination is a straightforward method to produce a variety of [ 18 F]fluoroarenes and [ 18 F]fluoroheteroarenes. To minimize the number of steps in the production of 18 F-labelled radiopharmaceuticals, we have developed a short and efficient azeotropic drying-free 18 F-labelling method using copper-mediated fluorination. Our goal was to improve the copper-mediated method to achieve wide substrate scope with good radiochemical yields with short synthesis time., Results: Solid phase extraction with Cu (OTf) 2 in dimethylacetamide is a suitable activation method for [ 18 F]fluoride. Elution efficiency with Cu (OTf) 2 is up to 79% and radiochemical yield (RCY) of a variety of model molecules in the crude reaction mixture has reached over 90%. Clinically relevant molecules, norepinephrine transporter tracer [ 18 F]NS12137 and monoamine transporter tracer [ 18 F]CFT were produced with 16.5% RCY in 98 min and 5.3% RCY in 64 min, respectively., Conclusions: Cu (OTf) 2 is a suitable elution agent for releasing [ 18 F]fluoride from an anion exchange cartridge. The method is fast and efficient and the Cu-complex is customizable after the release of [ 18 F]fluoride. Alterations in the [ 18 F]fluoride elution techniques did not have a negative effect on the subsequent labelling reactions. We anticipate this improved [ 18 F]fluoride elution technique to supplant the traditional azeotropic drying of [ 18 F]fluoride in the long run and to concurrently enable the variations of the copper-complex.