Synthesis of high specific activity C14-carboxyl indoleacetic acid and of C14-nitrile indoleacetonitrile

Existing methods that can be modified for the synthesis of C14 carboxyl-labeled indoleacetic acid were surveyed and the conditions necessary to obtain the maximum radiochemical yield from C14 -cyanide were determined. A major problem is the autoradiosensitivity of the product, which can be minimized by storage in dilute acetonitrile solution. Detailed procedures are given for a convenient one-day synthetic method for high purity indoleacetic acid and indoleacetonitrile with sufficient specific activity for use at physiological concentrations. The former was prepared with specific activities up to 16.9 mC/ mmole. At the highest specific activity levels, autoradiodecomposition during the course of synthesis apparently limits the yield obtained.