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Synthesis and Biological Evaluation of Novel 99mTc(CO)3-Labeled Thymidine Analogs as Potential Probes for Tumor Proliferation Imaging

Achieving a 99mTc 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 [99mTc(CO)3]+ core to prepare the corresponding 99mTc(CO)3 complexes in high yields. These complexes were hydrophilic and had good in vitro stability. Biodistribution of these complexes in mice bearing S180 tumors showed that all of them exhibited accumulation in the tumors, suggesting that they would be potential tumor imaging agents.