Simplified synthesis of N ‐(3‐[ 18 F]fluoropropyl)‐2 β ‐carbomethoxy‐3 β ‐(4‐fluorophenyl)nortropane ([ 18 F] β ‐CFT‐FP) using [ 18 F]fluoropropyl tosylate as the labelling reagent

A synthesis method has been developed for the labelling of N ‐(3‐[ 18 F]fluoropropyl)‐2 β ‐carbomethoxy‐3 β ‐(4‐fluorophenyl)nortropane ([ 18 F] β ‐CFT‐FP), a potential radioligand for visualization of the dopamine transporters by positron emission tomography. The two‐step synthesis includes preparation of [ 18 F]fluoropropyl tosylate and its use without purification in the fluoroalkylation of 2 β ‐carbomethoxy‐3 β ‐(4‐fluorophenyl)nortropane (nor‐ β ‐CFT). The final product is purified by HPLC. Optimization of the two synthesis steps resulted in a greater than 30% radiochemical yield of [ 18 F] β ‐CFT‐FP (decay corrected to end of bombardment). The synthesis time including HPLC‐purification was approximately 90 min. The radiochemical purity of the final product was higher than 99% and the specific radioactivity at the end of synthesis was typically 20 GBq/µmol. In comparison to alkylation by [ 18 F]fluoropropyl bromide, the procedure described here results in an improved overall radiochemical yield of [ 18 F] β ‐CFT‐FP in a shorter time. Copyright © 2005 John Wiley & Sons, Ltd.