Nicotinamide-substituted complexes as redox markers. 1. Synthesis and UV investigation of rhenium and technetium mixed-ligand systems

Abstract

In order to develop a redox delivery system for Tc radiotracers the synthesis of new nicotinamide and pyridinium salt‐substituted Re(V) mixed‐ligand complexes of the ‘3+1’ type is described. The complexation of 99/99mTc with these ligands was studied by thin layer chromatography and UV‐VIS spectroscopy. The reduction of the pyridinium salt with sodium dithionite to the 1,4‐dihydropyridine was carried out on the free ligand and on the complex. The stability of the 1,4‐dihydropyridines was observed by UV‐VIS spectrometry. © 1998 John Wiley & Sons, Ltd.

Potential Technetium Small Molecule Radiopharmaceuticals

“…Stability in human whole blood (in vitro) was found to be substantially better than in the original rat model. Various other examples of the 3 + 1 system developed originally by Johannsen and co-workers have been cited above in the previous sections on receptor specific molecules and illustrated in Figures d−g, 3b, 5c, 8d, and 8e. ,,,,, …”

“…The reduced analogues were only characterized in solution by the characteristic dihydropyridine absorbance at ca. 360 nm because of their sensitivity to reoxidation by air . Further research with these type of compounds may lead to redox-active 99m Tc radiotracers.…”

“…Regional myocardial ischemia was demonstrated in vivo in dogs by gamma camera imaging. 59 Kneiss et al 60 reported preliminary studies on nicotinamide-and pyridinium-derivatized monoden-tate thiols for preparing 99m Tc complexes as potential redox markers. A tridentate dithiolthioether chelate and the nicotinamide and methylpyridinium-substituted monodentate thiol were used to prepare Tc (V) O and Re (V) O 3 + 1 complexes.…”

“…360 nm because of their sensitivity to reoxidation by air. 60 Further research with these type of compounds may lead to redoxactive 99m Tc radiotracers.…”

“…76 However, this effect was found to be dependent on small 2d-g, 3b, 5c, 8d, and 8e. 15,18,19,26,34,60 B. Tc(CO) 3 + -Containing Chelates Almost all 99m Tc radiopharmaceuticals are based on Tc(V)oxo or octahedral Tc(III) cores. Organometallic low-oxidation state 99m Tc agents are less common, partly because of the difficulty of controlling the reduction of the Tc(VII) starting material to the reduced Tc(I) oxidation state.…”

Potential Technetium Small Molecule Radiopharmaceuticals

“…Stability in human whole blood (in vitro) was found to be substantially better than in the original rat model. Various other examples of the 3 + 1 system developed originally by Johannsen and co-workers have been cited above in the previous sections on receptor specific molecules and illustrated in Figures d−g, 3b, 5c, 8d, and 8e. ,,,,, …”

“…The reduced analogues were only characterized in solution by the characteristic dihydropyridine absorbance at ca. 360 nm because of their sensitivity to reoxidation by air . Further research with these type of compounds may lead to redox-active 99m Tc radiotracers.…”

“…Regional myocardial ischemia was demonstrated in vivo in dogs by gamma camera imaging. 59 Kneiss et al 60 reported preliminary studies on nicotinamide-and pyridinium-derivatized monoden-tate thiols for preparing 99m Tc complexes as potential redox markers. A tridentate dithiolthioether chelate and the nicotinamide and methylpyridinium-substituted monodentate thiol were used to prepare Tc (V) O and Re (V) O 3 + 1 complexes.…”

“…360 nm because of their sensitivity to reoxidation by air. 60 Further research with these type of compounds may lead to redoxactive 99m Tc radiotracers.…”

“…76 However, this effect was found to be dependent on small 2d-g, 3b, 5c, 8d, and 8e. 15,18,19,26,34,60 B. Tc(CO) 3 + -Containing Chelates Almost all 99m Tc radiopharmaceuticals are based on Tc(V)oxo or octahedral Tc(III) cores. Organometallic low-oxidation state 99m Tc agents are less common, partly because of the difficulty of controlling the reduction of the Tc(VII) starting material to the reduced Tc(I) oxidation state.…”

Potential Technetium Small Molecule Radiopharmaceuticals

“…Stability in human whole blood (in vitro) was found to be substantially better than in the original rat model. Various other examples of the 3 + 1 system developed originally by Johannsen and co-workers have been cited above in the previous sections on receptor specific molecules and illustrated in Figures d−g, 3b, 5c, 8d, and 8e. ,,,,, …”

“…The reduced analogues were only characterized in solution by the characteristic dihydropyridine absorbance at ca. 360 nm because of their sensitivity to reoxidation by air . Further research with these type of compounds may lead to redox-active 99m Tc radiotracers.…”

“…Regional myocardial ischemia was demonstrated in vivo in dogs by gamma camera imaging. 59 Kneiss et al 60 reported preliminary studies on nicotinamide-and pyridinium-derivatized monoden-tate thiols for preparing 99m Tc complexes as potential redox markers. A tridentate dithiolthioether chelate and the nicotinamide and methylpyridinium-substituted monodentate thiol were used to prepare Tc (V) O and Re (V) O 3 + 1 complexes.…”

“…360 nm because of their sensitivity to reoxidation by air. 60 Further research with these type of compounds may lead to redoxactive 99m Tc radiotracers.…”

“…76 However, this effect was found to be dependent on small 2d-g, 3b, 5c, 8d, and 8e. 15,18,19,26,34,60 B. Tc(CO) 3 + -Containing Chelates Almost all 99m Tc radiopharmaceuticals are based on Tc(V)oxo or octahedral Tc(III) cores. Organometallic low-oxidation state 99m Tc agents are less common, partly because of the difficulty of controlling the reduction of the Tc(VII) starting material to the reduced Tc(I) oxidation state.…”

Potential Technetium Small Molecule Radiopharmaceuticals

“…Stability in human whole blood (in vitro) was found to be substantially better than in the original rat model. Various other examples of the 3 + 1 system developed originally by Johannsen and co-workers have been cited above in the previous sections on receptor specific molecules and illustrated in Figures d−g, 3b, 5c, 8d, and 8e. ,,,,, …”

“…The reduced analogues were only characterized in solution by the characteristic dihydropyridine absorbance at ca. 360 nm because of their sensitivity to reoxidation by air . Further research with these type of compounds may lead to redox-active 99m Tc radiotracers.…”

“…Regional myocardial ischemia was demonstrated in vivo in dogs by gamma camera imaging. 59 Kneiss et al 60 reported preliminary studies on nicotinamide-and pyridinium-derivatized monoden-tate thiols for preparing 99m Tc complexes as potential redox markers. A tridentate dithiolthioether chelate and the nicotinamide and methylpyridinium-substituted monodentate thiol were used to prepare Tc (V) O and Re (V) O 3 + 1 complexes.…”

“…360 nm because of their sensitivity to reoxidation by air. 60 Further research with these type of compounds may lead to redoxactive 99m Tc radiotracers.…”

“…76 However, this effect was found to be dependent on small 2d-g, 3b, 5c, 8d, and 8e. 15,18,19,26,34,60 B. Tc(CO) 3 + -Containing Chelates Almost all 99m Tc radiopharmaceuticals are based on Tc(V)oxo or octahedral Tc(III) cores. Organometallic low-oxidation state 99m Tc agents are less common, partly because of the difficulty of controlling the reduction of the Tc(VII) starting material to the reduced Tc(I) oxidation state.…”