New Aspects of the Synthesis of closo-Dodecaborate Nitrilium Derivatives [B12H11NCR]− (R = n-C3H7, i-C3H7, 4-C6H4CH3, 1-C10H7): Experimental and Theoretical Studies

The preparation of novel nitrilium derivatives of closo-dodecaborate anion [B12H11NCR]−, R = n-C3H7, i-C3H7, 4-C6H4CH3, 1-C10H7 is described. Target compounds were obtained in good yields (up to 73%). The synthesis of target borylated nitrilium derivatives was characterised by the simplicity of the chemical apparatus and the absence of the necessity for the purification of desired compounds. The crystal structures of previously obtained [B12H11NCCH3]− and novel [B12H11NCC3H7]− were established with the help of X-ray structure analysis. DFT-analysis of several nitrilium derivatives [B12H11NCR]−, R = CH3, C3H7, 4-CH3C6H4 was carried out. The main peculiarities of the C≡N bond of the exo-polyhedral substituent were revealed in terms of bond lengths, bond orders and atomic charges. The LUMO orbitals of the systems considered were examined for understanding of the electrophilic nature of the nitrilium derivatives of the closo-dodecaborate anion.

Spontaneous Isomerization [trans-B20H18]2– → [iso-B20H18]2– during Cobalt(II) Complexation with Phenanthroline

Abstract

In this work, the cobalt(II) complexation with 1,10-phenanthroline (Phen) in the presence of the [trans-B20H18]2– anion has been studied. At a Co : Phen = 1 : 2 ratio in acetonitrile, a binuclear cobalt(II) complex with bridging chlorine atoms and the boron cluster anion as a counterion [(Phen)2Co(µ-Cl)2Co(Phen)2][trans-B20H18] has been isolated. However, during slow crystallization (within a month), spontaneous isomerization of [trans-B20H18]2– into [iso-B20H18]2– is observed. It has been established by X-ray diffraction analysis that in the crystal of the final compound [(Phen)2Co(µ-Cl)2Co(Phen)2][trans-B20H18]1/3[iso-B20H18]2/3, co-crystallization of both isomeric forms of the octadecahydroeicosaborate anion is observed for the first time. The presence of the iso form of the boron cluster anion is also confirmed by IR spectroscopy data: the spectrum of the product shows a band of stretching vibrations of the BHB bridge groups at 1773 cm–1, which is absent in the trans-form of the boron cluster.

New type of RNA virus replication inhibitor based on decahydro-closo-decaborate anion containing amino acid ester pendant group

In this work, a synthetic approach to prepare an example of new class of the derivatives of the closo-decaborate anion with amino acids detached from the boron cluster by pendant group has been proposed and implemented. Compound Na₂[B₁₀H₉–O(CH₂)₄C(O)–His–OMe] was isolated and characterized. This compound has an inorganic hydrophobic core which is the 10-vertex boron cage and the –O(CH₂)₄C(O)–His–OMe organic substituent. It has been shown to possess strong antiviral activity in vitro against modern strains of A/H1N1 virus at 10 and 5 µg/mL. The compound has been found to be non-cytotoxic up to 160 µg/mL. At the same time, the compound has been found to be inactive against SARS-CoV-2, indicating specific activity against RNA virus replication. Molecular docking of the target derivative of the closo-decaborate anion with a model of the transmembrane region of the M2 protein has been performed and the mechanism of its antiviral action is discussed.

Physiologically Active Compounds Based on Membranotropic Cage Carriers–Derivatives of Adamantane and Polyhedral Boron Clusters (Review)

Data on compounds based on cage structures―boron clusters (polyhedral boron hydrides, carboranes, metallacarboranes) and compounds of the adamantane series, which possess physiological activity, have been generalized. The main emphasis is placed on the antiviral activity of the compounds. The mechanism of the possible action of the replication inhibitors of influenza A virus strains is considered, the molecular model of viroporin inhibitors is discussed. The proposed model consists of a cage hydrophobic core that performs the function of a membranotropic carrier (a boron cluster or adamantane fragment), into which physiologically active functional groups are introduced. The relationship between the structure of the cage compound with the introduced substitute and the biologically active properties of this molecular structure has been analyzed.

Nucleophilic addition reactions to nitrilium derivatives [B12H11NCCH3]- and [B12H11NCCH2CH3]-. Synthesis and structure of closo-dodecaborate-based iminols, amides and amidines

The synthesis of the acetonitrilium and propioitrilium derivatives of closo-dodecaborate [B12H12]2- were discussed. The nucleophilic addition reactions of water, alcohols and secondary amines to the activated triple bond of the...

Primary Amine Nucleophilic Addition to Nitrilium Closo-Dodecaborate [B12H11NCCH3]-: A Simple and Effective Route to the New BNCT Drug Design

In the present work, a convenient and straightforward approach to the preparation of borylated amidines based on the closo-dodecaborate anion [B₁₂H₁₁NCCH₃NHR]-, R=H, Alk, Ar was developed. This method has two stages. A nitrile derivative of the general form [B₁₂H₁₁NCCH₃]^- was obtained, using a modified technique, in the first stage. On the second stage the resulting molecular system interacted with primary amines to form the target amidine products. This approach is characterised by a simple chemical apparatus, mild conditions and high yields of the final products. The mechanism of the addition of amine to the nitrile derivative of the closo-dodecaborate anion was studied, using quantum-chemical methods. The interaction between NH₃ and [B₁₂H₁₁NCCH₃]^- ammonia was chosen as an example. It was found that the structure of the transition state determines the stereo-selectivity of the process. A study of the biological properties of borylated amidine sodium salts indicated that the substances had low toxicity and could accumulate in cancer cells in significant amounts.

New Method for Synthesis of Substituted N-Borylated Dipeptides Based on Acetonitrile Derivative of the closo-Dodecaborate Anion

Abstract

A new multistage synthesis of the N-borylated dipeptide B12-PheGlyOH has been proposed. The approach is based on the reaction of nucleophilic addition of amino acid derivatives to the [B12H11NCCH3]– anion. The products of each stage have been characterized by multinuclear NMR spectroscopy, IR absorption spectroscopy, and ESI mass spectrometry.