Radioiodinated 5-iodothienyl-2-substituted long chain fatty acids for myocardial imaging

Thienyl-2-alkyl derivatives undergo facile iodination regiospecifically at the 5-position of the thiophene ring and are alternatives to iodophenyl agents. /sup 125/I-labeled 2-(17-oxoheptadecanoly)-5-iodothiophene (VIIIa) and /sup 125/I-labeled 2-(13-oxotridecanoyl)-5-iodothiophene (VIIIb) were prepared as model agents. The substrate was 2-(17-oxoheptadecanoyl)thiophene (VIa), in which the thiophene ring was attached to the terminal position of heptadecanoic acid. (VIa) was prepared by Friedel-Crafts condensation of 16-iodohexadecanoyl chloride, with thiophene followed by -I + CN/sup -/ ..-->.. -CN; Wolff-Kishner reduction; -CN + OH/sup -/ ..-->.. -COOH (VI). Regiospecific rho-(bis-(trifluoroacety 1)) thallation of (VIa), followed by treatment with KI gave 2-(17-oxoheptadecanoyl)-5-iodothiophene (VIIIa). Compound VIIIb was prepared in the same manner. Compounds Ia, b-VIIIa,b, were analyzed by TLC, IR, MS, NMR, and CandH. I-125-labeled (VIIIa) and (VIIIb) were prepared in the same manner. I-125 (VIIIb) showed high myocardial uptake in rats (4/group). Iodothienyl fatty acids may represent alternatives to iodophenyl substituted fatty acids for myocardial imaging.