Use of 2-[18F]fluoroethylazide for the Staudinger ligation - Preparation and characterisation of GABAA receptor binding 4-quinolones

The labelling reagent 2-[18F]fluoroethylazide was used in a traceless Staudinger ligation. This reaction was employed to obtain the GABAA receptor binding 6-benzyl-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid (2-[18F]fluoroethyl) amide. The radiotracer was prepared with a non-decay corrected radiochemical yield of 7%, a radiochemical purity >95% and a specific radioactivity of 0.9 GBq/μmol. The compound showed low brain penetration in normal rats. A series of fluoroalkyl 4-quinolone analogues with nanomolar to sub-nanomolar affinity for the GABAA receptor has been prepared as well.