Development of an automated system for synthesizing 18F-labeled compounds using [18F]fluoroethyl bromide as a synthetic precursor

An automated system was developed to synthesize F-18-labeled compounds using [F-18]fluoroethyl bromide ([F-18]FEtBr) as a synthetic precursor. The apparatus makes possible the following sequence of processes: (1) production of an aqueous solution of [F-18]fluoride ([F-18]F-), (2) recovery of [F-18]F- from target chamber, (3) drying of [F-18]F-, (4) formation and distillation of [F-18]FEtBr into a trapping vessel (5) alkylation of target compounds with [F-18]FEtBr, (6) High performance liquid chromatography purification and (7) formulation. [F-18]FEtBr, the synthetic precursor for fluoroethylation, was labeled via nucleophilic displacement of 2-trifluoromethanesulfonyloxy ethylbromide (BrCH2CH2OTf) with [F-18]F- and was purified from the reaction mixture by distillation. After the conditions for forming [F-18]FEtBr and drying [F-18]F- were optimized, [F-18]FEtBr was obtained in a radiochemical yield of 71 +/- 13% (n = 21, based on [F-18]F-, corrected for decay) and a radiochemical purity of 98 +/- 1.4% at end of the syntheses (EOS). Using this automated system, [F-18]fluoroethylspiperone ([F-18]FEtSP) was prepared by reacting spiperone with [F-18]FEtBr in a radiochemical yield and purity of 56 +/- 12% (n = 5, based on [F-18]FEtBr, corrected for decay) and 97 +/- 1.5% with a specific activity of 310 +/- 120 GBq/mumol at EOS. The total synthesis time was 55 +/- 2.3 min from the end of bombardment and the developed system has proved to be reliable and reproducible. (C) 2002 Elsevier Science Ltd. All rights reserved.