title: 18F fluoroethylations: different strategies for the rapid translation of 11C-methylated radiotracers.
abstract: BACKGROUND
  The translation of 11C-labeled compounds into their respective 18F-labeled derivatives is an important tool in the rapid development of positron emission tomography (PET) tracers. Thus, our aim was the development of a general method for the preparation of 18F-fluoroethylated compounds that (a) is applicable to a variety of precursors, (b) can be performed in a fully automated commercially available synthesizer and (c) enables this rapid translation of 11C-methylated tracers into their 18F-fluoroethylated analogs sharing the same precursor molecules.
  
  
  METHODS
  Ten methods for the preparation and purification of different 18F-fluoroethylating agents were compared. Subsequently, five 18F-labeled PET tracers were synthesized under fully automated conditions.
  
  
  RESULTS
  Radiochemical yields ranged from 34.4% to 60.8%, and time consumption ranged from 20 to 55 min for all methods. Use of 1-bromo-2-[18F]fluoroethane and distillation evinced as the method of choice.
  
  
  CONCLUSIONS
  We were able to develop a general method for the preparation of a variety of 18F-fluoroethylated molecules. The provided tool is solely based on commercially available resources and has the potential to simplify and accelerate innovative PET tracer development in the future.
authors.affiliation: Department of Nuclear Medicine, Medical University of Vienna, Vienna A-1090, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wadsak
authors.forename: Leonhard-Key
authors.initials: LK
authors.lastname: Mien
authors.forename: Dagmar E
authors.initials: DE
authors.lastname: Ettlinger
authors.forename: Harald
authors.initials: H
authors.lastname: Eidherr
authors.forename: Daniela
authors.initials: D
authors.lastname: Haeusler
authors.forename: Karoline-Maria
authors.initials: KM
authors.lastname: Sindelar
authors.forename: Bernhard K
authors.initials: BK
authors.lastname: Keppler
authors.forename: Robert
authors.initials: R
authors.lastname: Dudczak
authors.forename: Kurt
authors.initials: K
authors.lastname: Kletter
authors.forename: Markus
authors.initials: M
authors.lastname: Mitterhauser
mesh_terms: D002250:Carbon Radioisotopes / Q000737:chemistry*; D005462:Fluorine Radioisotopes / Q000737:chemistry*; D007553:Isotope Labeling / Q000295:instrumentation / Q000379:methods*; D008745:Methylation; D019275:Radiopharmaceuticals / Q000138:chemical synthesis*
chemical_list: D002250:Carbon Radioisotopes; D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals