Stability of the four 2-(p-nitrobenzyl)-trans-CyDTPA 88Y complexes

The unusual stereochemical influence on in vivo stability of the two C-Functionalized cyclohexyl diethylenetriamine-N,N,N',N'',N''-pentaacetic acid (CyDTPA) chelating agents, (CHX-A, CHX-B), recently reported warranted further investigation to determine why such differences in configuration produce such striking effects on the stability of the Yttrium complex. To this end, all four individual component stereoisomers of CHX-A and CHX-B were synthesized for a detailed investigation into their chelation chemistry. Results of transchelation measurements, serum stability studies, and in vivo femur deposition measurements with 88Y indicate that the 88Y-CHX-A chelates are significantly more stable, in vitro and in vivo, than the 88Y-CHX-B complexes. Additionally, significant difference in vivo between the 88Y complexes formed from the component enantiomeric ligands were observed. (orig.)