Pentacoordinate spirosilicate anion, bis(2,2′-biphenyldiyl)methylsilicate, synthesized by the lithium cleavage of dimethoxyethane

The reaction of spirobisilafluorene (1) with lithium in dimethoxyethane produces lithium 1-methyl-spirobisilafluorenide (2), a stable pentacoordinate silicon compound with five carbon ligands, and lithium 2-methoxyethoxide, which was identified by trapping with Ph₃SiCl to give Ph₃Si-OCH2CH2OCH3 (4). The X-ray crystal structure of 2 shows that the geometry at silicon is an idealized trigonal bipyramid, slightly distorted toward a square pyramid. Methanolysis of 2 cleaves a Si-aryl bond producing a methyl biphenylsilafluorene, 3. Crystal structures are reported for 3 and 4.     

Reaction of sulphate radical anion (SO<Superscript>.</Superscript><Subscript>4</Subscript><Superscript>-</Superscript>) with hydroxy-and methyl-substituted pyrimidines: a pulse radiolysis study

Reactions of sulphate radical anion (SO·₄ ^-) with 4,6-dihydroxy-2-methyl pyrimidine (DHMP), 2,4-dimethyl-6-hydroxy pyrimidine (DMHP), 6-methyl uracil (MU) and 5,6-dimethyl uracil (DMU) have been studied by pulse radiolysis at pH 3 and at pH 10. The transient intermediate spectra were compared with those from the reaction of hydroxyl radical (·OH). It is proposed that SO·₄ ^- produces radical cations of these pyrimidines in the initial stage. These radical cations are short-lived except in the case of DMHP where a relatively longer lived radical cation is proposed to be formed. When there is a hydrogen atom attached to the N(1) or N(3) position, a deprotonation from these sites is highly favored. When there is no hydrogen attached to these sites, deprotonation from a substituted methyl group is favored. At acidic pH, deprotonation from nitrogen is observed for DHMP, MU and DMU. At basic pH, the radical cation reacts with OH^- leading to the formation of OH adducts.     

聚合物硼氢阴离子还原剂的制备及其对酯的还原研究

氯型季我安盐型强碱性阴离子交换树脂７１１＾＃与硼氢化钾反应制得聚合物硼氢阴离子还原剂，树脂容量３．２ｍｍｏｌ ＢＨ４／ｇ。用于不同酯化合物的还原，操作简便，树脂可再生重复使用。     

Competitive Complexation of Lanthanide Cations by Xylitol and Nitrate Anion in Aqueous Solution: A Microcalorimetric Investigation

The apparent equilibrium constants and enthalpies of complexation of Nd³⁺, Sm³⁺, Eu³⁺, and Gd³⁺ by xylitol in aqueous solutions containing NaNO₃ at an ionic strength of 2.0 mol-kg^–1 have been determined by microcalorimetry at 25°C. Since nitrate anion weakly complexes the lanthanide cations, these values are analyzed in terms of competition between xylitol and NO ₃ ^- The method leads to the apparent equilibrium constants and enthalpies of complexation of the lanthanide cations by NO ₃ ^- at this particular ionic strength. Despite the difficulties encountered in characterizing rather weak associations, the results are, whenever comparison is possible, in good agreement with those obtained by direct microcalorimetry. The advantage of this competition method is that it can be used when the enthalpic effects are too weak and insufficiently concentration dependent for direct microcalorimetric determination. In the present case, it allows us to thermodynamically characterize the formation of SmNO ₃ ²⁺ and EuNO ₃ ²⁺ , processes we have not been able to study directly.     

Studies of poly-<Emphasis Type="Italic">L</Emphasis>-lysine-starch nanoparticle preparation and its application as gene carrier

Anion starch nanoparticle (StNP) with a diameter of 50 nm was prepared in water-in-oil microemulsion, with soluble starch as raw materials and POCl₃ as crosslinking agent. PLL-StNP was prepared by linking poly-L-lysine (PLL) on the surface of StNP. At the same time, the size of PLL-StNP and its stability in aqueous solution were checked by AFM. The analysis of plasmid DNA binding, DNase I enzymatic degradation, toxicity and transfection were done. We discovered that PLL-StNP may be used as non-virus nanoparticle gene carrier. And we developed the method of preparing PLL-StNP gene carrier and used it in cell transfection. As non-virus gene carrier, PLL-StNP has some advantages, such as large load of DNA, high transfection efficiency, low cell toxicity and biodegradability.     

4-(<Emphasis Type="Italic">N,N</Emphasis>-Dialkylthiocarbamoylthio)-5-nitropyrimidines as new potential nitric oxide donors

On heating at pH 6.86, 4-(N,N-dialkylthiocarbamoylthio)-5-nitropyrimidines are transformed into dithiolopyrimidines, which are either oxidized to bis(4-dialkylthiocarbamoylpyrimidin-5-yl) disulfides or converted into 4,6-diamino-5-nitropyrimidine derivatives with carbon disulfide elimination. The direction of the reaction is determined by the nature of a substituent in position 2 of pyrimidine and the bulk of the thiocarbamate substituent. Mechanistic schemes for these processes were proposed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2777–2783, December, 2005.     

Derivatives of the closo-dodecaborate anion and their application in medicine

The paper presents a comparative analysis of the possibilities and characteristic features of the application of various polyhedral boron compounds, viz., the closo-decaborate anion [B₁₀H₁₀]^2–, the closo-dodecaborate anion [B₁₂H₁₂]^2–, the carba-closo-dodecaborate anion [CB₁₁H₁₂]^–, carboranes C₂B₁₀H₁₂, and the bis(dicarbollide) complexes [M(C₂B₉H₁₁)₂]^– (M = Fe, Co, or Ni), in boron neutron capture therapy (BNCT) for cancer. The requirements on compounds used in BNCT are formulated and the advantages of the application of the closo-dodecaborate anion are considered. The data on the synthesis of various derivatives of the closo-dodecaborate anion, which either already found use in BNCT or are most promising in this field, are summarized. The possibilities of the application of agents derived from the closo-dodecaborate anion in medical diagnostics are discussed.     

Ph2S2-CaH2 in N-methyl-2-pyrrolidone as an efficient protocol for chemoselective cleavage of aryl alkyl ethers

CaH₂ was been found, for the first time, as a mild reducing agent to generate thiophenolate anion from Ph₂S₂ in N-methyl-2-pyrrolidone (NMP) for deprotection of aryl alkyl ethers. Excellent chemoselctivity was observed for substrates having chloro and nitro groups without displacement of the chlorine atom and the nitro group. Selective ether cleavage took place in the presence of α,β-unsaturated carbonyl and nitro groups without reduction and conjugate addition (to the α,β-unsaturated carbonyl group).     

Formal total synthesis of hemibrevetoxin B by a convergent strategy

Concise construction of the trans-fused 7/7/6/6 tetracyclic ether part of hemibrevetoxin B (1) was achieved by a convergent strategy based on coupling reaction of an acyl anion equivalent, reductive cyclization of an α,ε-dihydroxyketone, and introduction of a methyl group at the central ring junction by the Nicolaou method. The resultant tetracyclic ether was transformed into the known intermediate, which was already converted to 1 by the Yamamoto group, thereby completing the formal total synthesis of 1.     

Das erste Diniobat mit ‚isolierten’︁ Anionen: KLi4[NbO5]=K2Li8[Nb2O10]

The First Diniobate with ‘Isolated’ Anions: KLi₄[NbO₅]=K₂Li₈[Nb₂O₁₀] [1] . By heating of well ground mixtures of the binary oxides [K₂O, Li₂O, Nb₂O₅, K:Li:Nb=1.1:4.4:1, Pt-tube, 1100°C, 3d] colourless, triclinic single crystals of KLi₄NbO₅ have been prepared for the first time: space group P1 (Nr. 2) with a=816.9(2) pm, b=592.2(2) pm, c=589.7(2) pm, α=121.00(2)º, β=91.78(2)°, γ=99.23(2)°, Z=2. The crystal structure was solved by four-cycle diffractometer data [Mo-Kα , 1386 from 1386 I_o(hkl), R=3.4%, R_w=2.6%], parameters see text. Characteristic for this structure are “isolated” groups of [Nb₂O₁₀] and the tetrahedral coordination of Li(1), Li(2), and Li(3). Li(4) has a tetragonal-pyramidal coordination. The structural relations are deduced by Schlegel Diagrams. The Madelung Part of Lattice Energy, MAPLE, the Effective Coordination Numbers, ECoN and the charge distribution have been calculated and discussed.