Separation and characterization of the two diastereomers for [Gd(DTPA)-bz-NH2)(H2O)](super 2-), a common synthon in macromolecular MRI contrast agents: Their water exchange and isomerization kinetics

A demonstration that the diastereomer ratio for Ln(super III) DTPA derivatives remains constant throughout the lanthanide series, in contrast to Ln(super III) EPTPA derivatives, where it varies as a function of the cation size with a maximum for the middle lanthanides is presented. An HPLC analysis showed that the diastereomer ratio for Ln(super III) DTPA derivatives remains constant throughout the lanthanide series.