Application of Organosilicon Chemistry to the Synthesis of Gamma and Positron Emitting Radiotracers for Use in Nuclear Imaging Studies

Radiohalogenated compounds have been used in biomedical research and diagnostic nuclear medicine for many years. In the past ten years, interest in the development and use of radiohalogenated compounds has increased significantly, particularly for 123I,75Br, and 18F labeled compounds for imaging; 125I labeled compounds for autoradiography; as well as 131I, 125I, and 80mBr for radiotherapeutic applications. The radiohalogenation of compounds for these applications poses special synthetic constraints. In many cases, the radiohalogen must be incorporated at a specific position in the molecule in order to retain biological activity, and at a position which is metabolically stable towards dehalogenation. For radioiodinated and radiobrominated compounds, this often dictates that the radiotracer be an aryl-or vinylradiohalide. It is also important that these radiolabeled compounds be prepared in short reaction times, in high radiochemical yields, and at high specific activity. While high specific activity is generally desirable to reduce unwanted pharmacological or physiological side effects, high specific activity (on the order of 1,000 Ci/mmol) is required for receptor studies to prevent saturation of the receptor by carrier.