THE SYNTHESIS OF -(5-FLUORO-2-HYDROXYPHENYL)-METHYLENE-AMINOBUTYRIC ACID, AS A POTENTIAL RADIOLIGAND FOR THE GABA RECEPTOR IN THE BRAIN

A procedure for the synthesis of 4-(4-[C-11] -(5-fluoro-2-hydroxypheny l)-methylene-aminobutyric acid has been developed. The production enta iled a O-methylation of 5-fluoro-2-hydroxy-4'-hydroxybenzophenone with cyclotron produced [C-11]iodomethane in the presence of alkali and a subsequent Schiff reaction of 5-fluora-2- -hydroxy-4'-[C-11]methoxyben zophenone with gamma-aminobutyric acid. 5-Fluoro-2-hydroxy-4 '-hydroxy benzophenone was obtained by a demethylation of the 4'-metho-xyderivat ive with boron tribromide. Subsequent purification by HPLC and sterili sation by filtration gave 740 MBq(20 mCi) of an injectable solution. T he radiochemical yield (decay-corrected) from [C-11]iodomethane achiev ed 27%. The specific activity was 3.7 GBq/mu mol(100 mCi/mu mol) at th e end of the radiosynthesis (45 min from EOB). The preparations have b een demonstrated to be chemically and radiochemically pure by HPLC and TLC.