A carrier for a new tumor imaging agent, a bifunctional chelating agent (BCA)-coupled porphyrin (ATN-2), has been synthesized from protoporphyrin dimethyl ester in 4 steps. At first, the hydrobromination of protoporphyrin dimethyl ester is carried out to obtain a monobromo derivative. The derivative is treated with ethylene glycol. The resulting porphyrin has an ether group at the either 7-or 12-position of the ring. Metallation with GaCl
3 of the porphyrin having a ethylene glycol residue affords Ga-metalloporphyrin. Final condensation of the metalloporphyrin with diethylenetriaminepentaacetic acid (DTPA) gave BCA-coupled porphyrin (ATN-2). The chelation of ATN-2 with
111InCl
3 easily afforded [
111In] ATN-2. This agent was used for imaging transplantable pancreatic carcinoma in Syrian golden hamster at 72 h after postinjection. The efficacy of the new agent was compared with that of [
67Ga] citrate. The images with [
111In] ATN-2 were found to be clearer than those with [
67Ga] citrate. Therefore, ATN-2, a carrier for
111InCl
3, seems to be more useful for tumor imaging agents.
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