title: Comparison of bromo- and iodoalkyl triflates for 18F-radiolabeling of amines.
abstract: The use of 3-bromopropyl-1-trifluoromethanesulfonate and 3-iodopropyl-1-trifluoromethanesulfonate (triflates) as precursors for 18F-labeling of a secondary amine is described. This simple two step procedure, [18F]fluoride triflate displacement followed by N-alkylation, has been optimized using N-nordiprenorphine as the model substrate. The highest radiochemical yields (85%) for the triflate displacement reaction were obtained in THF using n-Bu4 NOH as the base. In comparing the two triflates no differences in the yields for this step were observed. In contrast, the yields for the fluoroalkylation step were increased more than 75% by using 1-[18F]fluoro-3-iodopropane rather than 1-bromo-3-[18F]fluoropropane. The highest yields for this N-alkylation reaction (35%) were achieved in DMF using N,N-diisopropylethylamine as the base. For both steps the observed yields are strongly dependent on the relative concentrations of the major reactants.
authors.affiliation: Edward Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110.
authors.forename: P L
authors.initials: PL
authors.lastname: Chesis
authors.forename: M J
authors.initials: MJ
authors.lastname: Welch
mesh_terms: D001679:Biogenic Amines; D005462:Fluorine Radioisotopes; D007553:Isotope Labeling / Q000379:methods*; D008698:Mesylates
chemical_list: D001679:Biogenic Amines; D005462:Fluorine Radioisotopes; D008698:Mesylates; C063885:3-bromopropyl-1-trifluoromethanesulfonate; C063886:3-iodopropyl-1-trifluoromethanesulfonate