Synthesis of a new rhenium labeled fatty acids and their ^99mTechnetium analogues for myocardial metabolism imaging

Rhenium model complexes and the respective Technetium-labeled fatty acids for myocardial metabolism imaging, were synthesized according to the “4+1” mixed-ligand approach and investigated in vitro and in vivo. The non-radioactive rhenium model complexes were characterized by NMR, IR, EA and the geometrical impact of the chelate unit on the integrity of the fatty acid structure was determined by X-ray analyses. The new fatty acid tracers contain the metal core in the oxidation states +3, well-wrapped in a trigonal-bipyramidal coordination moiety which is attached at the ω-position of a fatty acid chain as isocyano ligand in the case A. The compounds of group B contain the fatty acid moitie coupled on the tetradentate ligand. High heart extraction in perfused heart studies (up to 26% ID) and noticeable heart uptake of the ^99mTc tracers in vivo (using male Wistar rats) being in the order of 2% ID/g at 5min p.i. accompanied by a good heart to blood ratio of 8, confirms the target comparability.