Production and biological evaluation of [18F]-6-thia-14-fluoro-heptadecanoic acid

[(18)F]-6-thia-14-fluoro-heptadecanoic acid 3b, a free fatty acid, has been used in myocardial PET imaging. In order to establish an automated synthesis module for routine production in the country, a study was performed for optimization of the production conditions as well as making modifications.

[(18)F]Benzyl-14-Fluoro-6-thia-heptadecanoate 2b was prepared in no-carrier-added (n.c.a) form from Benzyl-14-tosyloxy-6-thia-heptadecanoate 1 in one step at 90 degrees C in Kryptofix2.2.2/[(18)F] with acetonitrile as the solvent followed by Silica column chromatography. The radiolabelled ester 2 was then hydrolysed to yield [(18)F]-6-thia-14-fluoro-heptadecanoic 3b. The final solution was concentrated using the C(18) SPE system and administered to normal rats for biodistribution and co-incidence imaging studies.

The synthesis took 15 min with overall radiochemical yield of 15-25% (EOS) and chemical-radiochemical purity of more than 90%. Automation was performed using a two-pot synthesis. The best imaging time was shown to be 140-180 minutes post injection.

Using this procedure a fast, reliable, automated synthesis for the cardial PET tracer, i.e. [(18)F]FTHA, can be obtained without an HPLC purification step.