Radiolabeling of biologically active molecules with the fac-<~(188)Re(CO)_(3)(H_(2)O)_(3)>~(+) unit has been of primary interest in recent years.Therefore,the tridentate ligands L_(1)~L_(4)(L_(1)=histidine,L_(2)= nitrilotriacetic,L_(3)= 2-picolylamine-N,N-diacetic acid,(L_(4)=) bis(2-pyridymethy)amine)were evaluated in radiochemical
reactions with the fac-(<~(188)Re(CO)_(3)(H_(2)O)_(3)>~(+)).These reactions yielded the
radioactive building blocks fac-(<~(188)Re(CO)_(3)L>)(L = L_(1)~L_(4)),which were identified by HPLC.Tricarbonyl complexes,with(lg P) values ranging from-2.23 to 2.18,were obtained in yields higher than 90%(using)(ligand) concentrations within the 1×10~(-5)~1×10~(-4) mol/L range.Competition studies with cysteine and
histidine revealed high stability for all of these radioactive complexes,and
biodistribution studies in mice indicated a fast rate of blood clearance and high rate of total radioactivity excretion occurring primarily through the renal-urinary pathway.In summary,complexes(L_(1)~L_(4)) are potent chelators for the future functionalization of biomolecules.
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