title: New approach for the synthesis of [18F]fluoroethyltyrosine for cancer imaging: simple, fast, and high yielding automated synthesis.
abstract: O-(2-[(18)F]fluoroethyl)-L-tyrosine ([(18)F]FET) is one of the first (18)F-labeled amino acids for imaging amino acid metabolism in tumors. This tracer overcomes the disadvantages of [(18)F]fluorodeoxyglucose, [(18)F]FDG, and [(11)C]methionine, [(11)C]MET. Nevertheless, the various synthetic methods providing (18)F[FET] exhibit a big disadvantage concerning the necessity of two purification steps during the synthesis including HPLC purification, which causes difficulties in the automation, moderate yields, and long synthesis times >60 min. A new approach for the synthesis of [(18)F]FET is developed starting from 2-bromoethyl triflate as precursor. After optimization of the synthesis parameters including the distillation step of [(18)F]-FCH(2)CH(2)Br combined with the final purification of [(18)F]FET using a simple solid phase extraction instead of an HPLC run the synthesis [(18)F]FET could be significantly simplified, shortened, and improved. The radiochemical yield (RCY) was about 45% (not decay corrected and calculated relative to [(18)F]F(-) activity that was delivered from the cyclotron). Synthesis time was only 35 min from the end of bombardment (EOB) and the radiochemical purity was >99% at the end of synthesis (EOS). Thus, this simplified synthesis for [(18)F]FET offers a very good option for routine clinical use.
authors.affiliation: Klinik für Nuklearmedizin, Universitätsklinikum Schleswig-Holstein Campus Kiel, 24105 Kiel, Germany. mzuhayra@nuc-med.uni-kiel.de
authors.forename: M
authors.initials: M
authors.lastname: Zuhayra
authors.forename: A
authors.initials: A
authors.lastname: Alfteimi
authors.forename: C Von
authors.initials: CV
authors.lastname: Forstner
authors.forename: U
authors.initials: U
authors.lastname: Lützen
authors.forename: B
authors.initials: B
authors.lastname: Meller
authors.forename: E
authors.initials: E
authors.lastname: Henze
mesh_terms: D001331:Automation; D002849:Chromatography, Gas; D009369:Neoplasms / Q000175:diagnosis*; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000302:isolation & purification; D052616:Solid Phase Extraction; D021241:Spectrometry, Mass, Electrospray Ionization; D014443:Tyrosine / Q000031:analogs & derivatives
chemical_list: C117289:O-(2-fluoroethyl)tyrosine; D019275:Radiopharmaceuticals; D014443:Tyrosine