The synthesis of radioiodinated carbohydrates and butyrothienones as potential imaging agents for computed tomography

Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) are two relatively new imaging techniques which allow for the non-invasive evaluation of biochemical processes in living subjects. Currently, SPECT is more widely accessible than PET, however, only a limited number of radiotracers have been successfully developed for imaging by SPECT. Two classes of radioiodinated compounds were developed as potential imaging agents for SPECT: 1) Radioiodinated carbohydrates for the assessment of glucose metabolism and 2) Radioiodinated butyrothienones for the evaluation of dopamine D₂ receptors in the brain. In both classes of compounds, the radioiodine was attached to an sp² hybridized carbon atom to provide radiotracers that were chemically and metabolically stable. Radioiodine incorporation was easily accomplished by radioiododestannylation of vinyl- and aryl-trialkylstannanes in the presence of an oxidizing agent. The incorporation of radioiodine into small molecules can have a significant effect on the biological activity of the resulting radiotracer because of the relatively large size and lipophilicity of the iodine atom. Preliminary evaluations of the effectiveness of the radioiodinated carbohydrates and butyrothienones as imaging agents are presented.