Boron-enriched star-shaped molecule via cycloaddition reaction

Preparation of dendritic carboranyl glycoconjugates as potential anticancer therapeutics

A series of carborane-appended glycoconjugates containing three and six glucose and galactose moieties have been synthesized via Cu(i)-catalyzed azide-alkyne [3 + 2] click cycloaddition reaction. The carboranyl glycoconjugates containing three glucose and galactose moieties were found to be partially water soluble whereas increasing the number to six made them completely water soluble. The evaluation of cytotoxicities and IC50 values of newly synthesized carboranyl glycoconjugates was carried out using two cancerous cell lines (MCF-7 breast cancer cells and A431 skin cancer cells) and one normal cell line (HaCaT skin epidermal cell line). All carboranyl glycoconjugates showed higher cytotoxicities towards cancerous cell lines than the normal cell line. Carboranyl glycoconjugates containing three glucose and galactose moieties (compounds 15 and 17) were found to be more cytotoxic than the glycoconjugates containing six glucose and galactose moieties (compounds 19 and 21). Moreover, administration of 100 μM concentrations of compounds 15 and 17 inhibited up to 83% of MCF-7 breast cancer cells and up to 79% A431 skin cancer cells. However, administration of similar concentrations of carboranyl glycoconjugates could inhibit only up to 35-45% of HaCaT normal epidermal cells. Thus, due to the higher cytotoxicities of dendritic carboranyl glycoconjugates towards cancer cells over healthy cells, they could potentially be useful for bimodal treatment of cancer such as chemotherapy agents and boron neutron capture therapy (BNCT) agents as well.

A self-catalyzed reaction of 1,2-dibenzoyl-o-carborane with hydrosilanes - formation of new hydrofuranes

The activation of Si-H bonds is a very important transformation both in organic and inorganic chemistry. Herein we report that 1,2-dibenzoyl-o-carborane (1) reacts with Si-H bonds, yielding new hydrofurane-type products. The mechanism of this Si-H bond activation was studied both experimentally and by DFT calculations, and supposedly proceeds in an FLP-type manner.

An amphiphilic block copolymer conjugated with carborane and a NIR fluorescent probe for potential imaging-guided BNCT therapy

A carborane-containing triblock copolymer conjugated with a near infrared (NIR) fluorescence probe has been synthesized via reversible addition fragmentation chain transfer (RAFT), ring open polymerization (ROP), and conjugations of a cyanine NIR dye.

Syntheses and reductions of C-dimesitylboryl-1,2-dicarba-closo-dodecaboranes

An investigation ofC-dimesitylboryl-ortho-carboranes, 1-(BMes₂)-2-R-1,2-C₂B₁₀H₁₀(1and2), reveals that the carborane is the electron-acceptor and the mesityl group is the electron-donor in these dyads.

Synthesis and fluorescence emission of neutral and anionic di- and tetra-carboranyl compounds

A new family of photoluminescent neutral and anionic di-carboranyl and tetra-carboranyl derivatives have been synthesized and characterized. The reaction of α,α'-bis(3,5-bis(bromomethyl)phenoxy-m-xylene with 4 equiv. of the monolithium salt of 1-Ph-1,2-C(2)B(10)H(11) or 1-Me-1,2-C(2)B(10)H(11) gives the neutral tetracarboranyl-functionalized aryl ether derivatives closo-1 and closo-2, respectively. The addition of the monolithium salt of 1-Ph-1,2-closo-C(2)B(10)H(11) to α,α,'-dibromo-m-xylene or 2,6-dibromomethyl-pyridine gives the corresponding di-carboranyl derivatives closo-3 and closo-4. These compounds, which contain four or two closo clusters, were degraded using the classical method, KOH in EtOH, affording the corresponding nido species, which were isolated as potassium or tetramethylammonium salts. All the compounds were characterized by IR, (1)H, (11)B and (13)C NMR spectroscopy, and the crystal structure of closo-3 was analysed by X-ray diffraction. The carboranyl fragments are bonded through CH(2) units to different organic moieties, and their influence on the photoluminescent properties of the final molecules has been studied. All the closo- and nido-carborane derivatives exhibit a blue emission under ultraviolet excitation at room temperature in different solvents. The fluorescence properties of these closo and nido-derivatives depend on the substituent (Ph or Me) bonded to the C(cluster), the solvent polarity, and the organic unit bearing the carborane clusters (benzene or pyridine). In the case of nido-derivatives, an important effect of the cation is also observed.

Application of cycloaddition reactions to the syntheses of novel boron compounds

This review covers the application of cycloaddition reactions in forming the boron-containing compounds such as symmetric star-shaped boron-enriched dendritic molecules, nano-structured boron materials and aromatic boronic esters. The resulting boron compounds are potentially important reagents for both materials science and medical applications such as in boron neutron capture therapy (BNCT) in cancer treatment and as drug delivery agents and synthetic intermediates for carbon-carbon cross-coupling reactions. In addition, the use of boron cage compounds in a number of cycloaddition reactions to synthesize unique aromatic species will be reviewed briefly.

New developments in the medicinal chemistry of carboranes

The advancements in the synthetic chemistry of carboranes and metallacarboranes have given rise to diversified uses in medicinal chemistry, resulting in many new medical applications. An overview of the medicinal chemistry of carboranes is presented emphasizing the use of nanoparticles, dendrimers, porphyrins and carbohydrates as boron carriers. A review with 80 references.

Synthesis and properties of carborane-appended C(3)-symmetrical extended pi systems

A series of C(3)-symmetric pi-conjugated compounds containing three to six o-carborane clusters have been synthesized by employing palladium-catalyzed Suzuki coupling reactions and palladium-catalyzed acetylation reactions, followed by silicon tetrachloride mediated trimerization reactions. Carborane-containing extended trimers were found to emit blue light. Incorporation of o-carborane clusters into extended pi-conjugated systems led to 22-70% enhancement of their relative fluorescence quantum yields. Decapitation of o-carborane clusters made these extended trimers water soluble, and their aqueous solutions were also found to be fluorescent, but with a reduced fluorescence intensity. The carborane-appended pi-conjugated compounds are found to be extremely thermally stable, and for some of these compounds only 10% mass loss occurred at temperatures close to 500 degrees C. The DSC thermograms of smaller C(cage)-appended trimers indicate the occurrence of solid-solid phase transitions.