by Isotopic Exchange

The 18F-labeled aromatic amino acid 6-fluoro-3,4-dihydroxy-L-phenylalanine (6-18F-fluoro-L-DOPA) is widely used as a radio-pharmaceutical in neurologic and oncologic PET. In this study, a novel approach to the preparation of carrier-added (CA) 6-18F-fluoro-L-DOPA in 3 radiosynthesis steps was developed and evaluated; in this approach, direct nucleophilic 18F fluorina-tion of a protected amino acid derivative was used. The method currently used for the routine preparation of 6-18F-fluoro-L-DOPA by electrophilic labeling is limited to the production of small amounts of activity at high costs. Alternative syntheses based on the advantage of large-scale production of nucleophilic 18F-fluoride, however, either have resulted in insufficient en-antiomeric purity or are difficult to automate because of the complexity of the necessary multiple steps. Methods: An isotopic exchange reaction on the precursor (2S,5S)-tert-butyl