Synthesis of 3,5-diisopropyl[carboxy-14C]salicylic acid and its 67CU complex

The synthesis of 3,5-diisopropyl[carboxy-14C]salicylic acid was achieved via Kolbe-Schmitt carboxylation of potassium 2,4-diisopropylphenolate. The yield of this acid was 81% based upon the weight of the product and 93% based upon radioactivity incorporated into the labeled acid which contains 98% 14C in the carboxyl group (specific activity = 5.1 μCi/mg). The labeled acid was characterized by ultraviolet spectrophotometry and purity established by thin-layer chromatography, autoradiography, and liquid scintillation counting. A 90% yield of the double labeled 14C, 67Cu-complex (specific activity = 4.6 μC/mg) was obtained using conditions developed with non-radioactive reactants. The presence of 67Cu in this complex was established using γ-ray emission spectrophometry.