ENANTIOSELECTIVE SYNTHESIS OF 6-[FLUORINE-18]-FLUORO-L-DOPA FROM NO-CARRIER-ADDED FLUORINE-28-FLUORIDE

Methods: A trimethylammonium veratraldehyde triflate was synthesized a nd used as a precursor for the asymmetric synthesis of 6-[F-18]fluoro- L-dopa. Results: Its nucleophilic fluorination with F-18-fluoride prod uced by the O-18(p,n)F-18 nuclear reaction on enriched O-18-water led to the corresponding no-carrier-added [F-18]fluoroveratraldehyde (45 /- 5% EOB). Diiodosilane was used to prepare the corresponding [F-18]f luorobenzyl iodide (36.5 +/- 5.3% EOB). Akylation of 1-tert-boc-2-tert -butyl-3-methyl-4-imidazolidinone with this electrophilic agent, hydro lysis and purification by preparative high-pressure liquid chromatogra phy made 6-[F-18]fluoro-L-dopa ready for human injection, in a 23% +/- 6% decay-corrected radiochemical yield. The enantiomeric purity and t he specific activity were above 96% and 1 Ci/mu mole respectively. Con clusion: Through this procedure, starting from 250 mCi of F-18-fluorid e, multimillicurie amounts (32 +/- 8.5 mCi) of no-carrier-added 6-[F-1 8]fluoro-L-dopa are now available at the end of synthesis (90 min) wit h a good radiochemical purity (more than 98%).