Propargyl‐Substituted Thiocarbamoylbenzamidines of Technetium and Rhenium: Steps towards Bioconjugation with Use of Click Chemistry

Abstract

A new propargyl‐substituted thiocarbamoylbenzamidine has been synthesized. The compound acts as a tetradentate ligand and forms stable complexes with {Re V O} 3+ and {Tc V O} 3+ cores. Click couplings of the resulting complexes with benzylazide lead to prototype triazole derivatives, which were analyzed by NMR and IR spectroscopy and mass spectrometry, as well as by X‐ray diffraction. A similar coupling procedure has been applied to an azido‐modified angiotensin‐II peptide, which gives the desired rhenium(V) bioconjugate in good yield. The ease of this coupling and the stability of the conjugate recommend such tetradentate thiocarbamoylbenzamidines also for clinically relevant bioconjugates with 99m Tc.