Carboranylphosphines: B9-Substituted Derivatives with Enhanced Reactivity for Anchoring to Dendrimers.

Invited for the cover of this issue are the groups and colleagues of Anne-Marie Caminade at the CNRS and University of Toulouse, Evamarie Hey-Hawkins at Leipzig University, and Agustí Lledós from the Autonomous University of Barcelona. The image depicts birds crowned by a carborane competing for access to food, to illustrate the steric hindrance encountered when grafting carboranes to dendrimers (artwork by Dr. Christoph Selg). Read the full text of the article at 10.1002/chem.202303867.

Carboranylphosphines: B9-Substituted Derivatives with Enhanced Reactivity for the Anchoring to Dendrimers.

Several ortho-carboranes bearing a phenoxy or a phenylamino group in the B9 position were prepared employing various protection and deprotection strategies. Following established protocols, dendritic compounds were synthesized from a hexachlorocyclotriphosphazene or thiophosphoryl chloride core, and possible anchoring options for the B9-substituted ortho-carboranes were investigated experimentally and theoretically (DFT). Furthermore, 1- or 1,2-phosphanyl-substituted carborane derivatives were obtained. The resulting diethyl-, diisopropyl-, di-tert-butyl-, diphenyl- or diethoxyphosphines bearing a tunable ortho-carborane moiety are intriguing ligands for future applications in homogeneous catalysis or the medicinal sector.

Dendritic Structures Functionalized with Boron Clusters, in Particular Carboranes, and Their Biological Properties.

The presence of a large number of boron atoms in boron clusters make them attractive tools for the treatment of cancer using boron neutron capture therapy (BNCT). Since the quantity of boron atoms present in the target cell directly affects the effectiveness of BNCT, the idea of gathering a high number of boron atoms in a single entity has emerged many years ago. In this perspective, using hyper-branched macromolecules such as dendrimers appears as an interesting solution. In this review, we will first present the synthesis of diverse dendritic entities (dendrimers, dendrons, and Janus dendrimers) that incorporate boron clusters, in particular carboranes, anywhere in their structure. Four parts of this review present the synthesis of dendrimers having boron clusters on the surface, or inside their structure, of dendrons and of Janus dendrimers, bearing boron clusters. Practically all these boronated dendritic structures were synthesized with the objective to study their biological properties, but in fact only a few of them have been tested against cancerous cells, and even a smaller number was tested in BNCT experiments. The biological experiments are discussed in the fifth part of this review. A good efficiency is generally observed with the boronated dendrimers, even in animal models, with an increase in their mean survival time (MST).