A facile direct nucleophilic synthesis of O-(2-[F]fluoroethyl)- l-tyrosine ([F]FET) without HPLC purification.

Due to favourable in vivo characteristics, its high specificity and the longer half-life of F (109.8 min) allowing for remote-site delivery, O-(2-[F]fluoroethyl)- l-tyrosine ([F]FET) has gained increased importance for molecular imaging of cerebral tumors. Consequently, the development of simple and efficient production strategies for [F]FET could be an important step to further improve the cost-effective availability of [F]FET in the clinical environment. In the present study [F]FET was synthesized via direct nucleophilic synthesis using an earlier developed chiral precursor, the Ni complex of an alkylated ( S)-tyrosine Schiff base, Ni-( S)- BPB-( S)-Tyr-OCHCHOTs. The purification method has been developed via solid phase extraction thereby omitting cumbersome HPLC purification. The suggested SPE purification using combination of reverse phase and strong cation exchange cartridges provided [F]FET in high chemical, radiochemical and enantiomeric purity and 35 % radiochemical yield (decay-corrected, 45 min synthesis time). The method was successfully automated using a commercially available synthesis module, Scintomics Hotbox. Based on the current results, the proposed production route appears to be well suited for transfer into an automated cassette-type radiosynthesizers without using HPLC. [ABSTRACT FROM AUTHOR]