New myocardial imaging agents: preparation of 15-(p-[123I]-iodophenyl)-6-tellurapentadecanoic acid from Na[123I] by a triazene decomposition reaction

A new radioiodinated tellurium fatty acid in which iodine-123 has been chemically stabilized by an attachment to the para position of a terminal substituted phenyl ring has been prepared for evaluation as a myocardial perfusion agent. The synthesis of 15-p-[123I]iodophenyl-6-tellurapentadecanoic acid was achieved by combining 9-(p-[123I]iodophenyl)nonyl chloride with sodium(methylvaleryl)telluride. The 9-(p-[123I]-iodophenyl)nonyl chloride was prepared by a triazene decomposition reaction involving hydrogen [123I]iodide treatment of the piperidinyltriazene of 9-(p-aminophenyl)nonyl chloride. Tissue distribution studies in female Fischer rats showed a rapid and pronounced uptake and prolonged retention. The initial heart-to-blood ratios were high and remained high for several hours. The iodine-125- and iodine-131-labeled analogs were also prepared by the same route and evaluated extensively in female Fischer rats for up to 5 days. Radiation absorbed dose estimates were calculated by the MIRD technique. These preliminary studies indicate that the iodine-123-labeled tellurium fatty acid is stable to in vivo deiodination and exhibits prolonged myocardial retention in rats and dogs