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Karborany jako lipofilowe farmakofory

Olejniczak A., Burzyńska-Pedziwiatr I.

Wiadomości Chemiczne

2007

[Z] 61, 7-8

567-589

Carboranes are boron cage systems in which one or more carbon atoms belong as an integral part to an elektron-delocalized borane framework. They are characterized by high boron content, remarkable thermal and chemical stability, spherical geometry and high hydrophobicity. Electropositivity of boron enables BH groups in carboranes to form unconventional hydrogen bonds defined also as proton - hydride bond. Another type of interaction was found for CH group of carborane - participating in hydrogen-bonded complexes, although these complexes are approximately 21 kJ/mol less stable than complexes formed by BH groups [2-8]. Proton - hydride bonds are formed mainly due to electrostatic interactions between boron--bound hydrogen atom bearing partial negative charge and hydrogen atom of a biomolecule bearing partial positive charge. It was found that carboranes forms proton - hydride bonds with biomolecules preferably with BH groups of the cage opposite to the carbon atom. Carboranes have been used as hydrophobic pharmacophores in design of analogues of biologically active compounds such as estradiol, retinoic acids, protein kinase C modulators and TNF-a activity modulators. Some of these carbo-rane containing biomolecules interact effectively with the corresponding receptor enzymes exhibiting equal or even higher biological activity than their endogenous counterparts and are characterized by remarkable resistance to catabolism.

Karborany i metalokarborany. Część 1, Karborany

Olejniczak A.

Wiadomości Chemiczne

2004

[Z] 58, 11-12

895--913

Polyhedral clusters containing boron, alone or in combination with other elements, have been know for nearly a century and intensive studies of their structures, bonding, and reactivity have been under way for more than half that period. Carboranes are boron cage system in which one or more carbon atoms belong as an integral part to an electron-delocalized borane framework. The term "carboranes" includes both closed polyhedral and open-cage structures. Polyhedral carboranes of general formula C2Bn-1Hn have been characterized from n=2 to n=12. One of the most striking features of the carboranes is the capability of the two carbon atoms and ten boron atoms to adopt the icosahedral geometry in which the carbon and boron atoms are hexacoordinate. This feature of the icosahedral structure gives rise to the unusual properties of these molecules and their derivatives. Because of their unique physical and chemical properties, carboranes have been used to prepare catalysts, radiopharmaceuticals, polymers and an assortment of coordination compounds and materials for nanotechnology. The medicinal chemistry of carboranes is centered on their use in boron neutron capture therapy of tumors (BNCT).