Rigid H4OCTAPA derivatives as model chelators for the development of Bi(III)-based radiopharmaceuticals.

Abstract

Octadentate ligands containing ethyl (H4OCTAPA), cyclohexyl (H4CHXOCTAPA) or cyclopentyl (H4CpOCTAPA) spacers were assessed as chelators for Bi(III)-based radiopharmaceuticals. The H4CHXOCTAPA chelator displays excellent properties, including 205/206Bi-nuclide radiolabelling under mild conditions, excellent stability in serum and in the presence of competing cations or H5DTPA. The poor performance of H4CpOCTAPA appears to be related to the stereochemical activity of the Bi(III) lone pair.