Synthesis of Small Peptides and Their Use as Bifunctional Chelating Agents in Diagnostic Radiopharmaceuticals

Three linear mercaptoacetyl tetrapeptides, MAG3-Leu-OH, MAG3-Phe-OH and MAG3-Tyr-OH, were synthesized via a liquid phase synthetic approach with high yields and high purities without using preparative HPLC technique. The obtained products could be radiolabeled easily with 99mTc under a mild condition and showed high stability in vitro and in vivo conditions. The scintigrams of the tested rabbit after injection of the radiolabeled products via mainline showed a normal biodistribution, which is definitely different from that of 99mTc-MAG3, indicating different routes of metabolization between these two radiochemicals.