Synthesis and Biological Evaluation of Novel (99m)Tc(CO)₃-Labeled Thymidine Analogs as Potential Probes for Tumor Proliferation Imaging.Achieving a (99m)Tc labeled thymidine radiotracer for single photon emission tomography (SPECT) is considered to be of interest.  In this study, four novel thymidine analogs, 6a, 6b, 6c and 6d, were successfully synthesized via "click reaction" route and then radiolabeled using a [(99m)Tc(CO)₃]⁺ core to prepare the corresponding (99m)Tc(CO)₃ complexes in high yields. 
(99m)Tc(CO)₃