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Objective: The strategic aim of this work is to create a fluorophore-labelled, clinically relevant exogenous NO donor carrying a boron-containing compound residue based on human serum albumin (HSA) for the implementation of combined NO-chemotherapy and boron-neutron-capture therapy. Methods: By selective modification of the Cys34 residue of albumin with a maleimide derivative of a fluorescent dye and subsequent N-homocysteinylation with a thiolactone derivative of homocysteine containing a clozo-dodecaborate residue, a nanoconstruct for boron-neutron-capture therapy was obtained. An analogue based on the natural modifier, boron-containing homocysteine thiolactone, was synthesised by alkylation of the amino group of thiolactone with a dioxonium derivative of clozo-dodecaborate. Post-synthetic modification of the lysine residues of the protein using the boron thiolactone of homocysteine provided the introduction of SH groups into the protein and the possibility of subsequent trans-S-nitrosylation of the protein using S-nitrosoglutathione. Results and Discussion: It was found that 2 M of NO was conjugated to 1 M of boron-containing HSA. Boron-containing S-nitrosothiol based on albumin homocysteinylamide, without epithermal neutron irradiation, was demonstrated to be more cytotoxic against human glioblastoma cell lines than the boron-containing albumin conjugate. Conclusions: Thus, the approach used allows obtaining a boron-enriched structure based on a biocompatible tumor-specific protein, containing a fluorescent label and an increased number of S-nitroso groups. It is necessary for the manifestation of a chemotherapeutic effect of the construct. The practical significance of this structure lies in the possibility of a cancer treatment, combining chemo- and boron-neutron capture therapy. [ABSTRACT FROM AUTHOR]

In catalytic reactions, the diverse binding sites of nanometals located in nanomaterials considerably influence the activity of nanocatalysts. In this study, the special nanostructure and charge distribution of halloysite nanotubes (HNTs) incorporating a weak reducing agent closo-dodecaborate (closo-[B12H12]2-) were leveraged to immobilize Au nanoparticles (NPs) on the inner and outer surfaces of HNTs. The introduction of closo-[B12H12]2- into HNTs was achieved via vacuum extraction and acid immersion. Subsequently, nanocatalysts loaded with Au NPs on the diverse surfaces of the HNTs were obtained from a direct reaction with a KAuCl4 solution. The Au NPs loaded on the inner surface of the HNTs were found to have highly dispersed and exhibited excellent catalytic activity in the reduction of nitroaromatics. At room temperature, the Au NPs loaded on the inner surface of the HNTs with a mass fraction of 0.02% showed a high turnover frequency value of 47.28 min-1 in a model reaction of the catalytic reduction of 4-nitrophenol to 4-aminophenol and exhibited excellent stability in cycling tests. Therefore, this study provides a new approach for synthesizing nanocomposites for various practical applications. [ABSTRACT FROM AUTHOR]

In der Massenspektrometrie werden häufig kurzlebige Ionen in der Gasphase beobachtet, die zuvor nicht in Lösung oder in der Bulkphase synthetisiert worden sind. Diese schwer zugänglichen Ionen werden daher oft primär als analytisch wertvoll für grundlegende Gasphasenstudien angesehen. Hier wird der Nachweis erbracht, dass die Produkte von Ionen‐Molekül‐Reaktionen in Massenspektrometern auf Oberflächen gesammelt werden können, um kondensierte Materie zu erzeugen und somit als Bausteine für die Synthese neuer Verbindungen zu dienen. Das hochreaktive Fragmentanion [B12Br11]− wurde in einem Massenspektrometer erzeugt und in Anwesenheit von molekularem Stickstoff in [B12Br11N2]− umgewandelt, gefolgt von seiner Massenselektion und sanften Deposition auf Oberflächen. Die Molekularstruktur des bisher nie zuvor synthetisierten [B12Br11N2]− wurde mit konventionellen Methoden der Molekularanalyse, einschließlich magnetischer Kernresonanz‐ und Infrarotspektroskopie, bestätigt. Das [B12Br11N2]−‐Ion ist auf Oberflächen und in Lösung bei Raumtemperatur stabil, aber Erhitzen führt zur Abspaltung von N2 und ermöglicht den Zugang zu dem hochreaktiven Zwischenprodukt [B12Br11]− in der kondensierten Phase, das beispielsweise als Reagenz für elektrophile aromatische Substitutionen weiterverwendet werden kann. Die Isolierung von [B12Br11N2]− erweitert somit das Repertoire der verfügbaren Diazo‐Ionen, die als vielseitige Zwischenprodukte bei verschiedenen chemischen Umwandlungen eingesetzt werden können. [ABSTRACT FROM AUTHOR]

Novel fluorescent 7-methoxy- and 7-(diethylamino)-coumarins modified with azido-group on the side chain have been synthesized. Their photophysical properties and single crystals structure characteristics have been studied. In order to demonstrate the possibilities of fluorescent labeling, obtained coumarins have been tested with closo-dodecaborate derivative bearing terminal alkynyl group. CuI catalyzed Huisgen 1,3-dipolar cycloaddition reaction has led to fluorescent conjugates formation. The absorption–emission spectra of the formed conjugates have been presented. The antiproliferative activity and uptake of compounds against several human cell lines were evaluated. [ABSTRACT FROM AUTHOR]

High-grade gliomas present a significant challenge in neuro-oncology because of their aggressive nature and resistance to current therapies. Boron neutron capture therapy (BNCT) is a potential treatment method; however, the boron used by the carrier compounds—such as 4-borono-L-phenylalanine (L-BPA)—have limitations. This study evaluated the use of boron-conjugated 4-iodophenylbutanamide (BC-IP), a novel boron compound in BNCT, for the treatment of glioma. Using in vitro drug exposure experiments and in vivo studies, we compared BC-IP and BPA, with a focus on boron uptake and retention characteristics. The results showed that although BC-IP had a lower boron uptake than BPA, it exhibited superior retention. Furthermore, despite lower boron accumulation in tumors, BNCT mediated by BC-IP showed significant survival improvement in glioma-bearing rats compared to controls (not treated animals and neutrons only). These results suggest that BC-IP, with its unique properties, may be an alternative boron carrier for BNCT. Further research is required to optimize this potential treatment modality, which could significantly contribute to advancing the treatment of high-grade gliomas.

In this work, a series of boronated amidines based on the closo -dodecaborate anion and amino acids containing an amino group in the side chain of the general formula [B 12 H 11 NHC(NH(CH 2 ) n CH(NH 3 )COOH)CH 3 ], where n = 2, 3, 4, were synthesized. These derivatives contain conserved α-amino and α-carboxyl groups recognized by the binding centers of the large neutral amino acid transporter (LAT) system, which serves as a target for the clinically applied BNCT agent para-boronophenylalanine (BPA). The paper describes several approaches to synthesizing the target compounds, their acute toxicity studies, and tumor uptake studies in vivo in two tumor models. The promising compound [B 12 H 11 NHC(NH(CH 2 ) 2 CH(NH 3 )COOH)CH 3 ]*3H 2 O demonstrates low toxicity (LD 50 in a range from 150 to 300 mg/kg) and excellent solubility and also shows selective uptake in experimental melanoma in laboratory mice (T/N ratio remained >3 up to 60 min post-injection, with a maximum T/N of 6.2 ± 2.8 at 45 min).

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.

A series of novel conjugates of cobalt bis(dicarbollide) and closo-dodecaborate with curcumin were synthesized by copper(I)-catalyzed azide-alkyne cycloaddition. These conjugates were tested for antibacterial activity. It was shown that all derivatives are active when exposed to Bacillus cereus ATCC 10702 and are not active against Gram-negative microorganisms and Candida albicans at the maximum studied concentration of 1000 mg/L. The conjugate of alkynyl-curcumin with azide synthesized from the tetrahydropyran derivative of cobalt bis(dicarbollide) exhibited activity against Gram-positive microorganisms: Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212 and the clinical isolate MRSA 17, that surpassed curcumin by 2–4 times.

A series of boron‐containing lipids were prepared by reactions of cyclic oxonium derivatives of polyhedron boranes and metallacarboranes (closo‐dodecaborate anion, cobalt and iron bis(dicarbollides)) with amine and carboxylic acids which are derived from cholesterol. Stable liposomal formulations, on the basis of synthesized boron‐containing lipids, hydrogenated soybean l‐α‐phosphatidylcholine and (HSPC) 1,2‐distearoyl‐sn‐glycero‐3‐phosphoethanolamine‐N‐[methoxy(polyethylene glycol)‐2000] (DSPE‐PEG) as excipients, were prepared and then characterized by dynamic light scattering (DLS) that revealed the formation of particles to be smaller than 200 nm in diameter. The resulting liposomal formulations showed moderate to excellent loading and entrapment efficiency, thus justifying the design of the compounds to fit in the lipid bilayer and ensuring ease of in vivo use for future application. The liposomal formulations based on cobalt and iron bis(dicarbollide)‐based lipids were found to be nontoxic against both human breast normal epithelial cells MCF‐10A and human breast cancer cells MCF‐7. [ABSTRACT FROM AUTHOR]

Water-soluble pteroyl-closo-dodecaborate conjugates (PBCs 1–4), were developed as folate receptor (FRα) targeting boron carriers for boron neutron capture therapy (BNCT). PBCs 1–4 had adequately low cytotoxicity with IC50 values in the range of 1~3 mM toward selected human cancer cells, low enough to use as BNCT boron agents. PBCs 1–3 showed significant cell uptake by FRα positive cells, especially U87MG glioblastoma cells, although the accumulation of PBC 4 was low compared with PBCs 1–3 and L-4-boronophenylalanine (L-BPA). The cellular uptake of PBC 1 and PBC 3 by HeLa cells was arrested by increasing the concentration of folate in the medium, indicating that the major uptake mechanisms of PBC 1–3 are primarily through FRα receptor-mediated endocytosis.

Noninvasive monitoring of boron agent biodistribution is required in advance of neutron capture therapy. In this study, we developed a gadolinium-boron-conjugated albumin (Gd-MID-BSA) for MRI-guided neutron capture therapy. Gd-MID-BSA was prepared by labeling bovine serum albumin with a maleimide-functionalized gadolinium complex and a maleimide-functionalized closo -dodecaborate orthogonally. The accumulation of Gd-MID-BSA in tumors in CT26 tumor-bearing mice reached a maximum at 24 h after the injection, as confirmed by T 1 -based MRI and biodistribution analysis using inductively coupled plasma optical emission spectrometry. The concentrations of boron and gadolinium in the tumors exceeded the thresholds required for boron neutron capture therapy (BNCT) and gadolinium neutron capture therapy (GdNCT), respectively. The boron concentration ratios of tumor to blood and tumor to normal tissues satisfied the clinical criteria, indicating the reduction of undesired nuclear reactions of endogenous nuclei. The molar ratio of boron to gadolinium in the tumor was close to that of Gd-MID-BSA, demonstrating that the accumulation of Gd-MID-BSA in the tumor can be evaluated by MRI. Thermal neutron irradiation with Gd-MID-BSA resulted in significant suppression of tumor growth compared to the group injected with a boron-conjugated albumin without gadolinium (MID-BSA). The neutron irradiation with Gd-MID-BSA did not cause apparent side effects. These results demonstrate that the conjugation of gadolinium and boron within the albumin molecule offers a novel strategy for enhancing the therapeutic effect of BNCT and the potential of MRI-guided neutron capture therapy as a promising treatment for malignant tumors.

Hydrogen has long been proposed as a versatile energy carrier that could facilitate a sustainable energy future. For an energy economy centred around hydrogen to function, a storage method is required that is optimised for both portable and stationary applications and is compatible with existing hydrogen technologies. Storage by chemisorption in borohydride species emerges as a promising option because of the advantages of solid-state storage and the unmatched hydrogen energy densities that borohydrides attain. One of the most nuanced challenges limiting the feasibility of borohydride hydrogen storage is the irreversibility of their hydrogen storage reactions. This irreversibility has been partially attributed to the formation of stable dodecahydro-closo-dodecaborates (Mn=1,2B12H12) during the desorption of hydrogen. These dodecaborates have an interesting set of properties that are problematic in the context of borohydride decomposition but suggest a variety of useful applications when considered independently. In this review, dodecaborates are explored within the borohydride thermolysis system and beyond to present a holistic discussion of the most important roles of the dodecaborates in modern chemistry.

Maleimide-conjugating closo-dodecaborate sodium form 5c (MID) synthesized by the nucleophilic ring-opening reaction of closo-dodecaborate-1,4-dioxane complex 2 with tetrabutylammonium (TBA) azide was found to conjugate to free SH of cysteine and lysine residues in BSA under physiological conditions, forming highly boronated BSA that showed high and selective accumulation in tumor and significant tumor growth inhibition in colon 26 tumor-bearing mice subjected to thermal neutron irradiation. [ABSTRACT FROM AUTHOR]

Synthesis and structure of silver and copper salts and complexes with polyhedral boron hydride anions, including closo-decaborate [B10H10]2−, closo-dodecaborate [B12H12]2−, 1-carba-closo- decaborate [1-CB9H10]−, carba-closo-dodecaborate [CB11H12]−, and cobalt bis(dicarbollide) [3,3′-Co(1,2-C2B9H11)2]− anions and their derivatives, are reviewed. The complexes demonstrate a wide variety of structural types, relating to both the metal coordination environment and coordination modes of boron hydride anions. The latter can range from strong coordination via the polyhedron triangular face including formation of 3c-2e MHB bonds in the case of the [B10H10]2− dianion, the structure of which contains two four-coordinated boron atoms, to very weak M…H interactions with the hydride atoms in the case of bulky [3,3′-Co(1,2-C2B9H11)2]− monoanion.

Abstract: Metal-free and Co(II)-phthalocyanines carrying eight dodecaborate substituents (96 boron atoms) on the peripheral positions were synthesized in a multistep reaction sequence. The first step of the preparation of metal-free and Co(II) target phthalocyanines was cyclotetramerization of 4-(3,5-dimethoxyphenoxy)phthalonitrile in pentanol in the presence of lithium pentanolate and Co(II) salt, respectively. After cleavage of methyl groups the reaction of (Bu4N)[B12H11O(CH2CH2)2O] with hydroxyphenoxy substituted phthalocyanines gives the novel phthalocyanines 7, 8 with eight dodecaborate units. The new phthalocyanine compounds were characterized by NMR, FT-IR and UV–VIS spectral data. The electrochemical investigations of cobalt(II) phthalocyanine together with Zn(II) derivative having identical substituents were studied. [Copyright &y& Elsevier]

[Display omitted] • B oron- c onjugated 4- i odo p henylbutanamide (BC-IP) was synthesized by conjugating 4-iodophenylbutanamide as an albumin ligand with a closo -dodecaborate. • BC-IP was water soluble and less cytotoxic. • The dissociation constant (K d) value of BC-IP to HSA was 148 ± 8 µM. • The boron concentration in the tumor reached a maximum of 11 μgB/g at 3 h after i.v. injection of BC-IP. The development of novel boron carriers applicable to various cancers is required for further expansion of boron neutron capture therapy (BNCT). In this study, we took advantage of the fact that serum albumin accumulates in tumors and developed a boron compound that interacts non-covalently with the serum albumin. 4-Iodophenylbutanamide was chosen as an albumin ligand and conjugated with closo -dodecaborate (b oron- c onjugated 4- i odo p henylbutanamide: BC-IP). BC-IP was found to be water soluble with low cytotoxicity. The IC 50 values of BC-IP were 475 µM for U87MG cells, 738 µM for HeLa cells, and > 1000 µM for A549 cells. The dissociation constant (K d) value of BC-IP to HSA was 148 ± 8 μM, while that of disodium closo -dodecaborate (4) was > 1000 μM. Significant tumor accumulation was observed in the U87MG tumor mouse model 3 h after injection. The boron concentration in the tumor reached a maximum of 11 μgB/g at 3 h and gradually decreased to 2.4 and 2.3 μgB/g at 12 and 24 h, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A new 2′-deoxyuridine modification, 3′,5′-bis-(dimethyl-tert-butylsilyl)-5-(3-(2-(dimethylamino)ethoxy)-3-methylbutyn-1-yl)-2′-deoxyuridine was effectively synthesized in four easy steps. Its reactivity toward a range of cyclic oxonium adducts of closo-dodecaborate and cobalt-bis-dicarbollide boron clusters was studied. The cleavage reactions of cluster oxonium rings by the N,N-dimethylamino group of the modified nucleoside led to 5-ethynyl-2′-deoxyuridine conjugates with [B12H12]2− and [Co(C2B9H11)2]−, respectively. Cytotoxicity of these new conjugates in several cell lines was examined. Closo-dodecaborate conjugates showed low cytotoxicity in all examined cell lines, an advantageous and preferred property for potential boron delivering drugs for the boron neutron capture therapy (BNCT) of tumors. [Copyright &y& Elsevier]

Conjugates of polyhedral boron hydrides with deoxyadenosine were synthesized by the opening of cyclic oxonium derivatives of closo-dodecaborate and cobalt bis(1,2-dicarbollide) with 2′-deoxyadenosine derivatives containing a nucleophilic group in the substituent at C(8). Biological studies of the derivatives obtained for cytotoxicity revealed that the derivatives based on closo-dodecaborate did not exhibit cytotoxicity. The conjugates obtained can be used in further biological trials as potential agents for boron neutron capture therapy of cancer. [ABSTRACT FROM AUTHOR]

The nucleophilic cleavage of 1-iodo-7-(dioxonium)decahydro- closo-dodecaborate ( 1) with sodium azide and thymidine or guanosine derivatives was studied. Compound 1 exhibits higher reactivity compared to the unsubstituted dioxonium derivative. The reactions of 1[NBu4] with 3′,5′-di( tert-butyldimethylsilyl)thymidine and 8-mercaptoguanosine afford the corresponding boron-containing nucleosides. [ABSTRACT FROM AUTHOR]

Abstract: New 2′-deoxyadenosine and adenosoine modifications: 8-[(2-dimethylaminoethyl)amino]-2′-deoxyadenosine and 8-[(2-dimethylaminoethyl)amino]adenosine were prepared and their reactivity towards cyclic oxonium adducts of closo-dodecaborate and cobalt-bis-dicarbollide was studied. The cleavage reactions of clusters oxonium rings by N,N-dimethylanio group of modified nucleosides led to the first [B12H12]2− and new [Co(C2B9H11)2]− conjugates with adenosine and 2′-deoxyadenosine respectively. The proposed methodology provides a convenient route for the synthesis of libraries of boron cluster modified adenosine and 2′-deoxyadenosine derivatives for biological screening. [Copyright &y& Elsevier]

Abstract: Cleavage of oxonium derivatives of [B12H12]2− by various S-nucleophiles was studied. Reactions of tetrabutylammonium 1-tetramethylene-(3-oxa)-oxonium-closo-undecahydrododecaborate with thiourea and a series of thiols resulted in novel B12-based mercaptane, aliphatic, aromatic and heteroaromatic sulfides with high yields under mild conditions. This approach was also used for the preparation of novel guanosine derivative of [B12H12]2−. [ABSTRACT FROM AUTHOR]

Abstract: The reactions of oxonium derivatives of [B12H12]2− with different glycerol-based nucleophiles were studied. A series of novel closo-dodecaborate-based glycerols with different net charges on the molecules were prepared. A structure of {2-[2-(4-(2, 3-dihydroxypropyl)-dipiperazinium-1-yl)-ethoxy]-ethoxy}-undecahydro-closo-dodecaborate was determined and the existence of different intermolecular H-bonds was shown. [Copyright &y& Elsevier]

Abstract: The first conjugates of closo-dodecaborate anion with nucleoside-thymidine were synthesized. The nucleophilic cleavage of dioxonium derivative of closo-dodecaborate by 3′,5′-bis(t-butyldimethylsilyl)-thymidine and “click” reaction between B12-based azide and 3N-(4-pentyn-1-yl)thymidine were appeared as convenient approaches towards the synthesis of this new class of nucleoside-based boron cluster conjugates. [Copyright &y& Elsevier]

Abstract: Practical method of synthesis of the 1,4-dioxane derivative of the closo-dodecaborate anion was developed. The cleavage of the dioxonium ring in [B12H11O(CH2CH2)2O]− with acetylenic alcohols gave rise to the preparation of closo-dodecaborate derivatives with terminal acetylene group. These compounds can be introduced into click reactions with phenylazide leading to the corresponding triazoles. The structures of (Bu4N)[B12H11O(CH2CH2)2O] and (Bu4N)2[B12H11(OCH2CH2)2OCH2Cp sp="0.25" />·0.5HOCH2Cetermined by single-crystal X-ray diffraction. [Copyright &y& Elsevier]

Abstract: The reactions of oxonium derivatives of [B12H12]2− with various amines were studied. A series of novel B12-species with ammonium group on the side chain was synthesized in high yield. A structure of tetrabutylammonium-[2-(2-morpholinium-ethoxy)-ethoxy]-undecahydro-closo-dodecaborate was determined and the existence of intramolecular N–H⋯O–B bond was shown. Using these reactions, novel boronated piperazines and amino acids were prepared. [Copyright &y& Elsevier]

High accumulation and selective delivery of boron into tumor tissues are the most important requirements to achieve efficient neutron capture therapy of cancers. We focused on liposomal boron delivery system to achieve a large amount of boron delivery to tumor. We succeeded in the synthesis of the double-tailed boron cluster lipids 4a-c and 5a-c, which has a B12H11S-moiety as a hydrophilic function, by S-alkylation of B12H11SH with bromoacetyl and chloroacetocarbamate derivatives of diacylglycerols. Size distribution of liposomes prepared from the boron cluster lipid 4b, dimyristoylphosphatidyl-choline, polyethyleneglycol-conjugated distearoylphosphatidylethanolamine, and cholesterol was determined as 100 nm in diameter by an electrophoretic light scattering spectrophotometer. Calcein-encapsulation experiments revealed that these boronated liposomes are stable at 37 °C in fetal bovine serum solution for 24 h. [ABSTRACT FROM AUTHOR]

• First 3-nitro-1,8-naphthalimide derivatives of nido‑ carborane and closo ‑dodecaborate. • Zwitterionic mitonafide bearing nido ‑carborane. • Synthesis of ammonium derivatives of nido ‑carborane via the nucleophilic breakdown reaction of oxonium rings. Methodologies for the synthesis of the first 3-nitro-1,8-naphthalimides bearing the nido ‑carborane and closo ‑dodecaborate moieties are reported. Series of boron containing 3-nitro-1,8-naphthalimides were synthesized by the reaction of 3-nitro-1,8-naphthalic anhydride with ammonium derivatives of nido ‑carborane and closo ‑dodecaborate anions. The nucleophilic ring-breakdown reaction of cyclic oxonium derivatives of nido ‑carborane with the tertiary dimethylamino group of mitonafide led to the novel boron-enriched mitonafides. The synthesized compounds are of interest as potential agents for boron neutron capture therapy for cancer. [Display omitted] [ABSTRACT FROM AUTHOR]

The closo -dodecaborate with multi-functional has shown its prominence in the fields of Supramolecular, hypergolic fuel, medicine, photoelectricity, ionic conduction and nano metal, and thus a timely and effective overview of its development status can maximize its infinite potential. [Display omitted] • First focus on multifunctional anion clusters closo -dodecaborate. • Review the progress of closo -dodecaborate based on intrinsic characteristic. • Prospect the application of closo -dodecaborate based on its physicochemical. The continuous discovery and derivatization of members of the closed borane family indicate that boron chemistry is about to embark on a development trajectory similar to that of carbon chemistry. Thus, three-dimensional, aromatic-like icosahedron closo -dodecaborate (denoted as boron cluster or closo -[B 12 H 12 ]2−), which has the most perfect structure and the most stable physical and chemical properties in the closed borane family, has begun to undertake important missions in the fields of medicine, energetic materials, host–guest chemistry, new energy, environmental treatment, and optoelectronic materials. Closo -[B 12 H 12 ]2− attracts increasing research attention because of its unique properties including being abundant hydrogen bond acceptors or donors, the unique chaotropic effect, 12 symmetrical modifiable B–H bonds, high ionic conductivity, high calorific value and weak reduction, and electronically adjustable photoelectric conversion. However, there are almost no reviews or books focusing on the progress and future of closo -[B 12 H 12 ]2−; this is detrimental to the full development of the potential of this functional anion cluster. Accordingly, this review summarizes the progress of closo -[B 12 H 12 ]2− in detail, aiming to uncover the mystery of closo -[B 12 H 12 ]2− and arouse the interest of researchers to promote the vigorous development of borane chemistry. [ABSTRACT FROM AUTHOR]

A series of water-soluble conjugates of 7-diethylamino-4-hydroxycoumarin with four different anionic polyhedral boron clusters was synthesized. The distribution coefficients (log D 7.4) as a measure of the ability to pass through the cell membrane for novel compounds were determined via a shake-flask methodology in n-octanol/aqueous (pH 7.4) buffer solution system. For two closo -dodecaborate modifications log D 7.4 displayed negative lipophilicity values. Conjugates of metallacarboranes containing Co and Fe as long as two 7,8-dicarba- nido -undecaborate coumarin anions were found to have appropriate lipophilicity for medicinal applications. • Novel anionic coumarin conjugates with several boron clusters were synthesized. • The first iron bis(1,2-dicarbollide) conjugate with coumarin is described. • Distribution coefficients (log D7.4) of prepared compounds were determined. • Some conjugates were found to have appropriate lipophilicity for medicinal use. [ABSTRACT FROM AUTHOR]

In the present work, a convenient and straightforward approach to the preparation of borylated amidines based on the closo -dodecaborate anion [B 12 H 11 NCCH 3 NHR]-, R=H, Alk, Ar was developed. This method has two stages. A nitrile derivative of the general form [B 12 H 11 NCCH 3 ] - 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 NH 3 and [B 12 H 11 NCCH 3 ] - 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.

Abstract: Reaction of [B12H11I]2− with 1,4-dioxane in presence of HBF4 resulted in 1-iodo-7-(tetramethylene-(3-oxa)-oxonium)-decahydro-closo-dodecaborate regioselectively with good yield. Its structure, especially 1,7-isomery, was definitely proved by NMR and XRD methods. This novel compound has two reactive centers, perspective either for nucleophlic cleavage of dioxonium ring and/or for substitution of iodine in various cross-coupling reactions. [Copyright &y& Elsevier]

Synthesis and characterization of novel coumarins containing carborane units were described. The breakdown reactions of cyclic oxonium derivatives of cobalt bis (1,2-dicarbollide) and closo -dodecaborate anions with a series of 7-hydroxy-3-substituted coumarins led to conjugates attached via C-7 position of the coumarin unit. The corresponding reactions of cobalt bis (1,2-dicarbollide) anion with 3-(4-hydroxybenzoyl)-7-methoxy-2H-chromen-2-one led to conjugates attached via C-3 position. Novel conjugates were isolated in the form of alkali metal salts. Therefore, these conjugates are of interest for the fluorescent study in aqua media. Series of coumarins conjugates with cobalt bis (1,2-dicarbollide) and closo -dodecaborate anions attached via C-7 or C-3 position of the coumarin ring were described. Image 1 • The synthesis of the first coumarins conjugates with COSAN was described. • The novel coumarins conjugates with closo -dodecaborate anion were synthesized. • Methods for the preparation of water-soluble coumarins were proposed. [ABSTRACT FROM AUTHOR]

Cyclic RGD (cRGD) peptide-conjugated boronated albumin was developed to direct toward integrin α v β 3, which overexpresses on many cancer cells. A stepwise conjugation of c[RGDfK(Mal)] and maleimide-conjugated closo -dodecaborate (MID) to bovine serum albumin (BSA) afforded cRGD-MID-BSA, which was noncytotoxic toward both U87MG and A549 cells. As compared with l-BPA, selective antitumor activity of cRGD-MID-BSA toward U87MG cells overexpressing integrin α v β 3 was identified after thermal neutron irradiation. In vivo fluorescence live imaging of Cy5-conjugated cRGD-MID-BSA and MID-BSA revealed that both cRGD-MID-BSA and MID-BSA similarly reached the maximum accumulation during 8-12 h after injection. The selective accumulation and retention of Cy5-cRGD-MID-BSA was more pronounced than Cy5-MID-BSA after 24 h. An in vivo boron neutron capture therapy (BNCT) study revealed that the cRGD peptide ligand combination enhanced accumulation of MID-BSA into tumor cells in U87MG xenograft models. The significant tumor growth suppression was observed in U87MG xenograft models at a dose of 7.5 mg [ 10 B]/kg after neutron irradiation.

Abstract: High accumulation and selective delivery of boron into tumor tissues are the most important requirements to achieve efficient neutron capture therapy of cancers. We focused on liposomal boron delivery system in order to achieve a large amount of boron delivery to tumor. We synthesized the double-tailed boron cluster lipid 4c according to our reported procedure with modification. Size distribution of liposomes prepared from the boron cluster lipid 4c, DMPC, PEG-DSPE, and cholesterol was determined as 100nm in diameter by an electrophoretic light scattering spectrophotometer. A high level of 10B concentration (22ppm) was observed in tumor tissue at 24h after the administration of boron liposomes. [Copyright &y& Elsevier]