Jan Nekvinda

Correction for ‘Synthetic routes to carbon substituted cobalt bis(dicarbollide) alkyl halides and aromatic amines along with closely related irregular pathways’ by Jan Nekvinda et al., Dalton Trans., 2024, 53, 5816–5826, https://doi.org/10.1039/D4DT00072B.

Carbon substituted cobalt bis(dicarbollide) alkyl halides [(1-X-(CH₂)_n-1,2-C₂B₉H₁₀)(1,2-C₂B₉H₁₁)-3,3′-Co]Me₄N (X = Br, I; n = 1–3) are prepared in high yields (>90%) from their corresponding alcohols without side skeletal substitutions.

The first crystallographic and quantum chemical evidence of B–H⋯π interaction in a protein–ligand complex is presented.

In this study we explore the effect on the electrochemical signals in aqueous buffers of the presence of hydrophilic alkylhydroxy and carboxy groups on the carbon atoms of cobalta bis(dicarbollide) ions. The oxygen-containing exo-skeletal substituents of cobalta bis(dicarbollide) ions belong to the perspective building blocks that are considered for bioconjugation. Carbon substitution provides wider versatility and applicability in terms of the flexibility of possible chemical pathways. However, until recently, the electrochemistry of compounds substituted only on boron atoms could be studied, due to the unavailability of carbon-substituted congeners. In the present study, electrochemistry in aqueous phosphate buffers is considered along with the dependence of electrochemical response on pH and concentration. The compounds used show electrochemical signals around −1.3 and +1.1 V of similar or slightly higher intensities than in the parent cobalta bis(dicarbollide) ion. The signals at positive electrochemical potential correspond to irreversible oxidation of the boron cage (the C2B9 building block) and at negative potential correspond to the reversible redox process of (CoIII/CoII) at the central atom. Although the first signal is typically sharp and its potential can be altered by a number of substituents, the second signal is complex and is composed of three overlapping peaks. This signal shows sigmoidal character at higher concentrations and may be used as a diagnostic tool for aggregation in solution. Surprisingly enough, the observed effects of the site of substitution (boron or carbon) and between individual groups on the electrochemical response were insignificant. Therefore, the substitutions would preserve promising properties of the parent cage for redox labelling, but would not allow for the further tuning of signal position in the electrochemical window.

This study presents the activity of a series of 1,8-naphthalimide–carborane/metallacarborane conjugates against Rhabditis sp. The carborane conjugates were the least active. Selected conjugates with cobaltacarborane (5 and 6) showed high activity. Their lethal concentration (LC₅₀) values are substantially lower than that of the drug mebendazole.

This review describes recent progress in the design and development of inhibitors of human carbonic anhydrase IX (CA IX) based on space‐filling carborane and cobalt bis(dicarbollide) clusters. CA IX enzyme is known to play a crucial role in cancer cell proliferation and metastases. The new class of potent and selective CA IX inhibitors combines the structural motif of a bulky inorganic cluster with an alkylsulfamido or alkylsulfonamido anchor group for Zn²⁺ ion in the enzyme active site. Detailed structure‐activity relationship (SAR) studies of a large series containing 50 compounds uncovered structural features of the cluster‐containing inhibitors that are important for efficient and selective inhibition of CA IX activity. Preclinical evaluation of selected compounds revealed low toxicity, favorable pharmacokinetics and ability to reduce tumor growth. Cluster‐containing inhibitors of CA IX can thus be considered as promising candidates for drug development and/or for combination therapy in boron neutron capture therapy (BNCT).

Invited for this month's cover is a collaboration from three institutes from the Czech Academy of Sciences: Institute of Inorganic Chemistry, Institute of Organic Chemistry and Biochemistry, and Institute of Molecular Genetics, and the University of Pardubice. The cover picture shows a family of potent and selective CA IX inhibitors that combines the structural motif of a bulky inorganic cobalt bis(dicarbollide) polyhedral ion with a propylsulfonamido anchor group. Read the full text of the article at 10.1002/cplu.202000574.

The diboration of substituted propargylic alcohols has been achieved using a bimetallic Pd/Cu catalyst system. The in situ formation of a pentrafluoroboronic acid intermediate sufficiently activates the C–O bond towards dual catalysis affording (Z)-allyl, vinyldiboronates stereoselectively.