title: Synthesis and characterization offac-Re(CO)3-aspartic-N-monoacetic acid, a structural analogue of a potential new renal tracer,fac-99mTc(CO)3(ASMA).
abstract: The reaction of an aminopolycarboxylate ligand,aspartic-N-monoaceticacid (ASMA), with [Re(CO)3(H2O)3]+was examined. The tridentate coordination of ASMA to this ReItricarbonyl precursor yieldedfac-Re(CO)3(ASMA) as a mixture of diastereomers. The chemistry is analogous to that of the TcItricarbonyl complex, which yieldsfac-99mTc(CO)3(ASMA) under similar conditions. The formation, structure, and isomerization offac-Re(CO)3(ASMA) products were characterized by HPLC,1H NMR spectroscopy, and X-ray crystallography. The two majorfac-Re(CO)3(ASMA) diastereomeric products each have a linear ONO coordination mode with two adjacent five-membered chelate rings, but they differ in the endo or exo orientation of the uncoordinated acetate group, in agreement with expectations based on previous studies. Conditions have been identified for the expedient isomerization offac-Re(CO)3(ASMA) to a mixture consisting primarily of one major product. Because different isomeric species typically have different pharmacokinetic characteristics, these conditions may provide for the practical isolation of a single99mTc(CO)3(ASMA) species, thus allowing the isolation of the isomer that has optimal imaging and pharmacokinetic characteristics. This information will aid in the design of future99mTc radiopharmaceuticals.
authors.affiliation: Department of Radiology and Imaging Sciences, Emory University, 1364 Clifton Rd, Atlanta, GA 30322, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Klenc
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Lipowska
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Taylor
authors.forename: Luigi G
authors.initials: LG
authors.lastname: Marzilli
keywords: Aminopolycarboxylate ligands; Imaging agents; Isomer resolution; Ligand design; Rhenium