The synthesis of D-trihydroxyllysine-based oligopeptides as a hydrophilic scaffold and its application to the synthesis of bifunctional chelating agents for use as bone tracers.

An effective hydrophilic scaffold composed of D-trihydroxyllysine-based oligopeptides and its application in the synthesis of the various (111)In-DTPA conjugates with mono- to penta-bisphosphonate units for use as bone tracers are described. The D-trihydroxyllysine derivative with three orthogonal protecting groups was conjugated with functional devices at the gamma position and allowed oligomerization based on peptide chemistry. The radiopharmaceutical complexes of (111)In(III) with selected chelators, 4 and 8, were suitable for bone imaging. These results show that D-trihydroxyllysine 2 was an effective building block for the synthesis of multivalent ligands applicable to medical use.