New approach for the synthesis of [18F]fluoroethyltyrosine for cancer imaging: simple, fast, and high yielding automated synthesis.
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.
Zuhayra
M
M
Klinik für Nuklearmedizin, Universitätsklinikum Schleswig-Holstein Campus Kiel, 24105 Kiel, Germany. mzuhayra@nuc-med.uni-kiel.de
Alfteimi
A
A
Forstner
C Von
CV
Lützen
U
U
Meller
B
B
Henze
E
E
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
C117289:O-(2-fluoroethyl)tyrosine; D019275:Radiopharmaceuticals; D014443:Tyrosine