title: A three-step radiosynthesis of 6-[(18)  F]fluoro-L-meta-tyrosine starting with [(18)  F]fluoride.
abstract: The radiosynthesis of 6-[(18)  F]fluoro-L-m-tyrosine has generally been performed by electrophilic radiofluorination, which exhibits several drawbacks. In the present work, a three-step radiochemical synthesis is described starting from [(18)  F]fluoride. The synthetic sequence, including isotopic exchange, Baeyer-Villiger oxidation, and hydrolysis, were examined comparing four fluorobenzophenone derivatives as labeling precursors. Of those, (2S,5S)-tert-butyl 5-(5-acetyl-2-fluorobenzyl)-2-tert-butyl-3-methyl-4-oxoimidazolidine-1-carboxylate (1a) and (2S,5S)-tert-butyl 2-tert-butyl-5-(2-fluoro-5-(2,2,2-trifluoroacetyl)benzyl)-3-methyl-4-oxoimidazolidine-1-carboxylate (1d) proved to be the most suitable ones. 6-[(18)  F]Fluoro-L-m-tyrosine was obtained with overall radiochemical yields of 8-13% and an enantiomeric excess of up to 98%.
authors: Forschungszentrum Jülich GmbH, Institut für Neurowissenschaften und Medizin, INM-5: Nuklearchemie, 52425, Jülich, Germany.
authors: Johnny
authors: J
authors: Castillo Meleán
authors: Johannes
authors: J
authors: Ermert
authors: Heinz H
authors: HH
authors: Coenen
mesh_terms: D060326:Chemistry Techniques, Synthetic; D005459:Fluorides / Q000737:chemistry*; D005462:Fluorine Radioisotopes / Q000737:chemistry*; D054879:Halogenation; D006868:Hydrolysis; D010084:Oxidation-Reduction; D011854:Radiochemistry; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: C496696:6-fluoro-3-hydroxyphenylalanine; D005462:Fluorine Radioisotopes; D014443:Tyrosine; D005459:Fluorides
keywords: 6-[18 F]fluoro-L-m-tyrosine; Baeyer-Villiger oxidation; fluorine-18; isotopic exchange; positron emission tomography