Radiosynthesis of 10-(2-[18F]fluoroethoxy)-20(S)-camptothecin as a potential positron emission tomography tracer for the imaging of topoisomerase I in cancers

The preparation of 10-(2-[ 18 F]fluoroethoxy)-20( S )-camptothecin, a potential positron emission tomography tracer for the imaging of topoisomerase I in cancers, is described. 10-(2-[ 18 F]Fluoroethoxy)-20( S )-camptothecin was synthesized by the [ 18 F]fluoroalkylation of the corresponding hydroxy precursor molecule with 2-[ 18 F]fluoroethyl bromide ([ 18 F]FEtBr) in dimethylsulfoxide (DMSO) at 55 °C for 20 min; this was followed by purification using high performance liquid chromatography (HPLC) with a total preparation time of 60 min. The overall radiochemical yield was approximately 5.4–12 % (uncorrected), and the radiochemical purity was above 96 %.