A copper-promoted reductive homocoupling reaction, for the first time used for a metal complex, allowed obtaining a new kind of complexes with the encapsulated metal ions, C-C conjugated bis-clathrochelates. These compounds demonstrate extremely high transcription inhibition activity in the T7 RNA polymerase system with values of IC50 reaching as low as the submicromolar range, which places them among the most potent metal-based transcription inhibitors.
The review presents the following main trends and the perspectives of application of the transition metal clathrochelates in medicine and biochemistry: encapsulation of radioactive metal ion for diagnostics and therapy; imaging agents for MRI; antidotes and prolonged pharmaceuticals; pharmaceuticals for boron neutron capture therapy; antihelminthic and antiparasitic detergents; antioxidants; membrane transport of the metal ions; interaction of the cage metal complexes with nucleic acids and the potential of their self assembling reactions in immunology and molecular biology (recognition of antibodies, antigens and DNA sites); design of HIV inhibitors for the therapy.
IntroductionMacrobicyclic cage complexes with encapsulated metal ions (clathrochelates) are representatives of a relatively new class of compounds with unusual chemical, physical, and physicochemical properties. The keen interest of sci entists working in several fields of chemistry and bio chemistry in these compounds is caused by the unique properties of a metal ion completely encapsulated in the three dimensional cavity of a macropolycyclic ligand and largely isolated from the external factors. 1 The availability of these compounds combined with their chemical (kinetic and thermodynamic) and photo chemical stabilities, intensive coloration, low toxicity, and the ability to undergo reversible redox reactions and to form ordered molecular structures imply practical use of metal cage complexes as functional materials, dyes, lumi nescent probes, biologically active compounds, and elec Voloshin et al.tron carriers in catalytic redox systems. The unique struc ture of clathrochelates, i.e., the presence of a metal ion completely isolated from the environmental factors, makes them attractive research subjects for photochemistry, magnetochemistry, and electrochemistry. In bioinorganic chemistry, these compounds may be of interest as models of the active sites of enzymes and siderochromes. Clathro chelates are unique rigid cage molecules that are selec tively self assembled from simple precursors under mild conditions. This makes them promising "molecular scaf folds" for the synthesis of polyfunctional and polytopic molecular and supramolecular systems. 2-5The chemical variability of metal cage complexes al lows both apical (by choosing functional substituents in cross linking groups) 6,7 and ribbed (by nucleophilic sub stitution of reactive substituents in the chelating α di oximate fragments 2,3,8-17 ) functionalization.
Apical functionalizationRibbed functionalization Y, Q are cross linking atoms, R 1 -R 5 are functionalizing substituents.In this paper we attempted to highlight the main well developed and perspective trends in biochemical and me dicinal applications of clathrochelates, i.e., cage com plexes with encapsulated transition metal ions.
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