Simple determination of 90Sr in water in environmental radioactivity survey

Derivatives of dodecahydro-closo-dodecaborate(2-) anion were proposed as boron-rich compounds for boron-neutron capture therapy (BNCT) of malignant tumours. Labeling of such tumour-targeting compounds with radioisotopes would facilitate the investigation of their pharmacokinetics and help to optimize patient treatment protocols. Earlier, we reported the feasibility of labeling of closo-dodecaborate(2-) by isotopic exchange in molten acetamide. In this study, the feasibility of low-temperature isotopic exchange in the system [¹²⁵I]iodide - bis(triethylammonium) undecahydro-12-iodo-closo-dodecaborate was investigated. Our attempts to perform the exchange in solvents such as methylene chloride, acetone and acetonitrile in the presence of phase-transfer catalysts were unsuccessful. However, copper mediated exchange in aqueous media was possible. Isotopic exchange of triethylammonium undecahydro-12-iodo-closo-dodecaborate provided a 90-95% labeling yield after heating for three and half hours at 100 °C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nitrosation of Dodecahydro-closo-Dodecaborate Anions in Aqueous and Nonaqueous Solutions

Nitrosation of dodecahydro-closo-dodecaborate anions with nitrous acid in an aqueous solution and with isoamyl nitrite and nitrosyl chloride in nonaqueous solutions was studied. The main reaction product is the mononitrosoundecahydro-closo-dodecaborate anion. Conditions were selected for the preparation of the nitroso-substituted anion in the highest yield as alkylammonium, tetraphenylphosphonium, and alkali-metal salts. The salts were studied using IR, UV, and ¹¹B NMR spectroscopy.     

Synthesis of new building blocks based on the <Emphasis Type="Italic">closo</Emphasis>-dodecaborate anion

The reactions of the dioxonium derivative of closo-dodecaborate(12) with aromatic aldehydes and esters containing O- and N-nucleophilic centers were studied. These reactions were used to synthesize new closo-dodecaborate-based building blocks containing aldehyde and acidic groups. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1961–1963, September, 2008.     

Synthesis of a (B12H11S) containing glucuronoside as potential prodrug for BNCT

A B₁₂H₁₁SH²⁻ containing glycoside of glucuronic acid has been prepared, for possible use as prodrug in BNCT. The synthesis was carried out by the Koenigs-Knorr reaction of the acetylated glucopyranosyluronate bromide with the nucleophile cyanoethylthioundecahydro-closo-dodecaborate(2−). After removal of the cyanoethyl-group, deacetylation and saponification of the reaction product tris(tetramethylammonium)-[S-(β-d-glucuronate)-thio] undecahydro-closo-dodecaborate(3−) could be prepared.     

Synthesis of closo-dodecaborate based nucleoside conjugates

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.     

Synthesis and NMR spectra of the hydroxyundecahydro-closo-dodecaborate [B12H11OH]2− and its acylated derivatives

Tetrabutylammonium hydroxyundecahydro-closo-dodecaborate was obtained in high yield via [B₁₂H₁₁NMP]^–(NMP =N-methylpyrrolidone) by the modified method. [B_i2H₁₁OH]^2– is easily acylated by aromatic acyl chlorides to give novel compounds [B₁₂H₁₁OCOAr]^2– in high yields. All the compounds were characterized by standard and special NMR methods.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 722–725, March, 1996.     

New boron-containing 2′-deoxyadenosines

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.     

Reactions of oxonium derivatives of [B12H12] with amines: Synthesis and structure of novel B12-based ammonium salts and amino acids

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.     

Synthesis and structure of novel closo-dodecaborate-based glycerols

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.     

Non-covalent assemblies of negatively charged boronated porphyrins with different cationic moieties

A unique approach to non-covalent electron and energy transfer is described that is based on the formation of salt bridges between oppositely charged porphyrin units. A new class of electrostatically linked dimeric and pentameric porphyrins was synthesized by interaction of novel anionic boron containing porphyrins such as 5-(benzamidodecahydro-closo-dodecaborate)-10,15,20-triphenylporphyrin (N1) and meso-tetrakis-benzamidodecahydro-closo-dodecaborate)porphyrin (N2) and a variety of cationic meso-tetraarylporphyrin units. A bipyridine linked dimer (N1 · bpy · N1) was also prepared by employing N,N′-dimethyl-4,4′-bipyridinium (bpy) as a spacer between two mono-anionic species. A quinone-porphyrin dyad was also prepared for electron or energy transfer demonstration. All the synthesized assemblies were characterized by NMR, IR, UV-Vis, and mass spectroscopy. Significant spectral changes occurred in the absorption spectra of these non-covalent porphyrin assemblies compared to those of the reference monomers, indicating the presence of electronic interaction between the adjacent porphyrin units. Resonance light scattering was also used to study the formation of these assemblies in solution.     

Syntheses based on 1-iodo-7-(dioxonium)decahydro-closo-dodecaborate

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.     

Fragmentation of B12H11S-R(2−) in electrospray mass spectrometry

The electrospray ionization (ESI) mass spectrometry (MS) of (3-carboxyethyl)-thio-undecahydro-closo-dodecaborate(2−) shows the appearance of additional peaks corresponding to B₁₂H₁₁SH(2−) and B₁₂H₁₁(1−). Their origin can be traced to fragmentation reactions in the skimmer-CID region and the ion trap of the spectrometer.     

Synthesis and structure of 1-iodo-7-dioxonium-decahydro-closo-dodecaborate

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.     

Ethynylmonocarba-closo-dodecaborates: M[12-HCC-closo-1-CB11H11] and M[7,12-(HCC)2-closo-1-CB11H10] (M = Cs, [Et4N])

Cesium and tetraethylammonium salts of the ethynyl functionalized monocarba-closo-dodecaborate anions [12-HCC-closo-1-CB₁₁H₁₁]⁻ and [7,12-(HCC)₂-closo-1-CB₁₁H₁₀]⁻ were obtained by desilylation of [Et₄N][12-Me₃SiCC-closo-1-CB₁₁H₁₁] and [Et₄N][7,12-(Me₃SiCC)₂-closo-1-CB₁₁H₁₀], respectively. Their thermal properties were examined by differential scanning calorimetry. The compounds were characterized by multi-NMR, IR, and Raman spectroscopy, (−)-MALDI mass spectrometry, and elemental analysis. Single-crystals of Cs[12-HCC-closo-1-CB₁₁H₁₁] and [Et₄N][7,12-(HCC)₂-closo-1-CB₁₁H₁₀] were studied by X-ray diffraction. The discussion of the spectroscopic and structural properties is supported by data derived from theoretical calculations using density functional theory as well as perturbation theory.     

Intramolecular cyclization of 2-(o-carboran-1-yl) methylthio-3-cyanopyridines in basic conditions

Substituted 2-(o-carboran-1-yl)methylthio-3-cyanopyridines and-pyrimidines undergo Thorpe-Ziegler cyclization under the influence of KOH in DMF to give the corresponding thienopyridines and thienopyrimidines. The reaction is complicated by a side reaction in which thecloso-carborane nucleus is converted to anido-system. The yield of thienopyridines containing acloso-carborane unit is increased by introduction of an acceptor substituent in the pyridine ring. Destruction of thecloso-carborane nucleus is not observed with the pyrimidine derivatives. The structures of the series of new carborane-containing thienopyridines and pyrimidines was confirmed by spectroscopic methods.A. N. Nesmeyanov Institute of Elementoorganic Chemistry, Russian Academy of Sciences, Moscow 117813. N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 790–793, June, 1998.     

Radiolabeling of 1-[N',N'-bis(2-chloroethyl)-4-aminophenyl]-N-methyl-fullereno-C60-[1,9-c]pyrrolidine with 125I

Summary A procedure for labeling of a fullerene derivative 1-[N',N'-bis(2-chloroethyl)-4-aminophenyl]-N-methyl-fullereno-C₆₀-[1,9-c]pyrrolidine (C₆₀-C₁₃H₁₈N₂Cl₂) with ¹²⁵I is reported. The compound was first iodinated with a large excess of iodine monochloride and then radiolabeled by isotopic exchange with Na¹²⁵I in a toluene-water two-phase system. The dependence of the radiolabeling yield on the reaction temperature and exchange time was examined. The radiolabeling yield of the compound was as high as 94% after heating for 2 hours at 130 °C.     

Dodecaborate cluster lipids with variable headgroups for boron neutron capture therapy: Synthesis, physical-chemical properties and toxicity

We have prepared two new boron-containing lipids with potential use in boron neutron capture therapy of tumors. These lipids consist of a diethanolamine frame with two myristoyl chains bonded as esters, and a butylene or ethyleneoxyethylene unit linking the doubly negatively charged dodecaborate cluster to the amino function of the frame, obtained by nucleophilic attack of the amino on the tetrahydrofurane and dioxane derivatives, respectively, of closo-dodecaborate. The latter cluster lipid can form liposomes at 25 °C whereas the former lipid at this temperature assembles into bilayer disks. Both lipids form stable liposomes when mixed with suitable helper lipids. The thermotropic behavior was found to be different for the two lipids, with the butylene lipid showing sharp melting transitions at surprisingly high temperatures. Toxicity in vitro and in vivo varies greatly, with the butylene derivative being more toxic than the ethyleneoxyethylene derivative.     

N-arylammonio- and N-pyridinium-substituted derivatives of dodecahydro-closo-dodecaborate(2-)

We report two methods for preparing N-arylammonio, N-pyridyl and N-arylamino dodecaborates: heating of the tetrabutylammonium salt of dodecahydro-closo-dodecaborate(2-) with aryl and pyridyl amines, or nucleophilic attack of [closo-B₁₂H₁₁NH₂]²⁻ on a strongly deactivated aromatic system. With aryl amines we obtained [1-closo-B₁₂H₁₁N(R¹)₂C₆H₅]⁻ (R¹ = H, CH₃). With 4-(dimethylamino)pyridine, [1-closo-(B₁₂H₁₁NC₅H₄)-4-N(CH₃)₂]⁻, with a bond between the boron and the pyridinium nitrogen, was obtained. A presumable mechanism for this kind of reactions is reported. By nucleophilic substitution, two products, [1-closo-(B₁₂H₁₁NHC₆H₃)-3,4-(CN)₂]²⁻ and [1-closo-(B₁₂H₁₁NHC₆H₂)-2-(NO₂)-4,5-(CN)₂]²⁻, were formed with 4-nitrophthalonitrile and 1-chloro-2,4-dinitrobenzene gave [1-closo-(B₁₂H₁₁NHC₆H₃)-2,4-(NO₂)₂]²⁻. For [1-closo-B₁₂H₁₁N(CH₃)₂C₆H₅]⁻ and [1-closo-(B₁₂H₁₁NHC₆H₃)-2,4-(NO₂)₂]²⁻ single crystal X-ray structures were obtained.     

Practical synthesis of 1,4-dioxane derivative of the closo-dodecaborate anion and its ring opening with acetylenic alkoxides

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)₂OCH₂CCH] · 0.5HOCH₂CCH were determined by single-crystal X-ray diffraction.     

Thermodynamic properties of chitosan dodecahydro-closo-dodecaborate

Combustion enthalpies of chitosan dodecahydro-closo-dodecaborate corresponding to ?13194 kJ/mol are measured via combustion in an AKS-3M automatic calorimeter. The standard enthalpy of formation corresponding to ?5223 kJ/mol is calculated from the resulting experimental data.