Anti-cancer activity of m-carborane-containing trimethoxyphenyl derivatives through tubulin polymerization inhibition

m-Carborane-containing compound 1a was identified as a cell growth inhibitor from a random screening of a boron compound library. As 1a is a mixture of diastereomers due to the presence of two chiral carbons, we designed achiral derivatives 2-4 and studied the structure-activity relationships of the methoxy groups on the benzene ring. 3,4,5-Trimethoxybenzyl derivative 2a and 3,4,5-trimethoxybenzoyl derivative 3a showed more potent anti-cancer activity against the human breast cancer cell line MDA-MB-453 than lead compound 1a. Compound 3a inhibited tubulin polymerization in a dose-dependent manner.

Comparative analysis of fluorine-containing mesogenic derivatives of carborane, bicyclo[2.2.2]octane, cyclohexane, and benzene using the Maier-Meier theory

Two series of related three-ring nematoges with Δε > 0 and containing 12-vetex carborane (A), 10-vertex carborane (B), bicyclo[2.2.2]octane (C), cyclohexane (D) and benzene (E) were prepared and investigated as additives to 6-CHBT nematic host and in the pure form (series 2). Dielectric results were analyzed with the Maier-Meier relationship to gain an understanding of behavior of additives in nematic solutions. Molecular parameters for each nematogen were obtained at the B3LYP/6-31G(d,p) level of theory in the host's dielectric medium, and dielectric data was used as the only experimental parameter to calculate apparent order parameter Sapp and the Kirkwood factor g. The results demonstrated that compounds in series 1 stabilize the nematic phase (high Sapp) of the host more than additives in series 2 (low Sapp), and carbocycles C and D are more effective (higher Sapp) than carborane analogues A and B (lower Sapp). The method provides insight into behavior of additives in nematic solutions and is useful for comparative analysis of a series of compounds or a series of hosts.

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.

Ring-alkyl connecting group effect on mesogenic properties of p-carborane derivatives and their hydrocarbon analogues

The effect of the phenyl–alkyl connecting group on mesogenic properties of several series of isostructural compounds containing p-carborane (A and B), bicyclo[2.2.2]octane (C), and benzene (D) was investigated using thermal and optical methods. Results demonstrated that mesophase stability in the series containing A–D follows the order (Alk)CH₂CH₂– < (Alk)OOC– < (Alk)CH₂O– < (Alk)COO–. Surprisingly, the connecting groups (Alk)CH₂CH₂– and (Alk)OOC– destabilize the mesophase significantly stronger for carboranes (A and B) than for carbocyclic derivatives (C and D). Analysis indicates that this effect may have quadrupolar and conformational origin.

Synthesis of a new class of carborane-containing star-shaped molecules via silicon tetrachloride promoted cyclotrimerization reactions

Symmetrical star-shaped molecules with carborane clusters on the periphery have been synthesized in good yields via silicon tetrachloride mediated cyclotrimerization reactions of 9-benzyl derivatives of carboranes with acetyl group substitution on the benzene ring. Facile functionalization of these symmetrical core structures with 1-iodoheptane and trivinylchlorosilane produce compounds which could be used as liquid crystalline substances and precursors for synthesis of higher order carbosilane dendrons.