Synthesis, radiotechnetium labelling, and comparison of biologic behavior of longer-chain analogs of methylene diphosphonate.

Polymethylene diphosphonic acids of different chain lengths ( n = 2, 3, and 10) were synthesized and labeled with technetium-99m. Their biologic behavior was compared with that of Tc-99m-labeled methylene diphosphonate (MDP) in experimental animals. With n = 2 (ethylene diphosphonic acid), the compound resembled MDP in bone affinity. The longer-chain analogs had lower bone affinity.