Nucleophilic addition reactions to the activated triple bond of the nitrilium derivatives of the closo -dodecaborate anion were studied.

Novel fluorescent 7-methoxy- and 7-(diethylamino)-coumarins modified with azido-group on the side chain have been synthesized. Their photophysical properties and single crystals structure characteristics have been studied. In order to demonstrate the possibilities of fluorescent labeling, obtained coumarins have been tested with closo-dodecaborate derivative bearing terminal alkynyl group. Cu^I catalyzed Huisgen 1,3-dipolar cycloaddition reaction has led to fluorescent conjugates formation. The absorption–emission spectra of the formed conjugates have been presented. The antiproliferative activity and uptake of compounds against several human cell lines were evaluated.

The sulfa-Michael addition reaction was applied for the two-step synthesis of o-carboranyl cysteine 1-HOOCCH(NH₂)CH₂S-1,2-C₂B₁₀H₁₁ from the trimethylammonium salt of 1-mercapto-o-carborane and methyl 2-acetamidoacrylate. To avoid the decapitation of o-carborane into its nido-form, the “free of base” method under mild conditions in a system of two immiscible solvents toluene-H₂O was developed. The replacement of H₂O by ²H₂O resulted in carboranyl-cysteine containing a deuterium label at the α-position of the amino acid 1-HOOCCD(NH₂)CH₂S-1,2-C₂B₁₀H₁₁. The structure of the protected o-carboranyl cysteine was determined by single-crystal X-ray diffraction. The obtained compounds can be considered as potential agents for the Boron Neutron Capture Therapy of cancer.