一类2(1H)-喹喔啉衍生物的电子轰击质谱分析

以邻苯二胺为原料合成表征了一类喹喔啉衍生物；1-烷基-3-甲基-2（1H）-喹喔啉-2-酮（1-alkyl-3-methly-2(1H)-quinoxalin-2-one，简称AMQ，其中alky=H、CH3、Et、n-C3H5、n-C5H11、n-C16H33)。用电子轰击电离质谱（EI-MS）和核磁共振谱图（^1H-NMR)鉴定了AMQ，研究了不同取代基对这类化合物EI-MS谱图的影响，分析得到一些裂解规律。结果表明：所有样品谱图中均有芳香化合物的特征CnHn^ 系列峰m/z78，65，52，39和（或）m/z77、76、64、63、51、50、38、37。对于末取代的样品及低级烷烃取代的样品，谱图中的基峰为分子离子峰，对于取代基中碳数大于等于3的样品。谱图中的基峰不是分子离子峰，分子离子峰强度随着碳数的增加而降低。这些样品一般容易发生骨架重排，丢失一分子CO，生成1-烷基-2-甲基苯并哒唑正离子。此外，还讨论了谱图中其它的一些碎片离子峰。这对于研究和指导喹喔啉衍生物 的合成，探讨它们在药效及结构特征与生理活性的关系等方面具有重要的应用价值和理论意义。     

Conformational analysis of 2-oxo-1,2,3,4,-tetrahydropyridine and its alkyl- and phenyl-substituted derivatives

The molecular geometries and inversion barriers of the rings in 2-oxo-1,2,3,4-tetrahydropyridine and its alkyl-substituted (Me, Et, Prⁱ, or Bu^t) and phenyl-substituted derivatives were calculated by the molecular mechanics method. The introduction of substituents has no substantial effect on the equilibrium conformation of the heterocycle (a distorted sofa). For 4-alkyl- and 3-alkyl-substituted derivatives (except for 4-Me and 4-Et derivatives), an axial orientation of the alkyl group is more favorable. The phenyl substituents have equatorial and axial orientations at postions 4 and 3, respectively. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1584–1586, September, 1997.     

Basicity and structure of 5-hydroxybenzimidazoles in nitromethane

Examination of the acid-base properties of 5-hydroxybenzimidazoles has shown them to exist in nitromethane as the 5-hydroxy-tautomers. Substituents in the 2-position have a predominantly inductive effect on the basicity of the 3-nitrogen, rationalized as in other nitrogen heterocycles by the proximity of the substituents to the reaction center.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. The Research Institute for Intermediates and Dyes, 103787 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 421–425, February, 1992.     

Crystal structure and characterization of the bis(n-benzyl-benzotriazole-n3)-dichloro Co(II) complex: CoCl2(C6H4N3CH2Ph)2

The structure of [CoCl₂(C₆H₄N₃CH₂Ph)₂] has been determined by X-ray crystallography. It is also characterized by elemental analysis, IR and electronic spectroscopy, and by thermogravimetric differential thermal analysis. It crystallizes in the monoclinic system, space group C2/c, with lattice parameters a = 16.133(3) , b = 11.355(2) , c = 15.637(3) , = 117.22(3)°, and Z = 8. The crystal structure of the title compound consists of monomeric molecules of [CoCl₂(C₆H₄N₃CH₂Ph)₂] with slightly distorted tetrahedron geometry for the CoCl₂N₂ chromophore. The thermal gravimetry (TG) data indicate that there are four decomposition steps with five endothermic peaks. The final product of the thermal decomposition is CoCl₂. Elemental analysis and the electronic and IR spectra are in agreement with the structural data.Original Russian Text Copyright © 2004 by F. Jian, H. Wang, and H. XiaoTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 723–728, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

A Protein‐Resistant Matrix for Electrochemical Based Recognition Assays

In this work, two well known polymers, carboxymethyl dextran and poly(ethyleneglycol), are used for easily producing a platform for electrochemical affinity assays, avoiding nonspecific adsorption of proteins. In this way, modified electrode surfaces able to bind a recognition agent are constructed through simple and reliable reactions.     

Synthesis and Transformation of Methyl 2‐(6‐Hydroxy‐2‐phenylpyrimidin‐4‐yl)acetate: Simple Preparation of Pyrimidines with Heterocyclic Substituents

A simple and efficient synthesis of four new substituted pyrimidines, compounds 9a – d , from the title compound 3 is described. Conversion of 3 to methyl (E)‐3‐(dimethylamino)‐2‐(6‐methoxy‐2‐phenylpyrimidin‐4‐yl)prop‐2‐enoate ( 4 ), followed by condensation with various dinucleophiles according to the ‘enaminone methodology’, afforded the target compounds 9 in medium‐to‐good yields.     

Thermal stability and degradation of starch derivatives

Thermal behaviour of different starch derivatives, i.e. starch esters and ethers having degree of substitution (DS) in the range of 0.02–0.18 were studied. Potato, maize and wheat starches were used. Measurements were carried out by coupled thermal analysis/ mass spectrometry method (STA-MS) in air atmosphere. The major DTG peak during the investigation for starch derivatives is observed below 300°C. The mass loss up to a temperature of 300°C is about 50%. The most abundant ions found areH₂O⁺ and CO₂ ⁺. For the studied starch derivatives with a low degree of substitution (DS<0.18) no correlation was found between thermal stability and the level of substitution regardless of the nature of substitution.     

Silver (I)-promoted asymmetric halohydrin reaction of chiral N-enoyl-2-oxazolidinones: scope and limitations

The halohydrin reaction of chiral N-enoyl-2-oxazolidinones 1 by halogen (Br₂/I₂) and water were efficiently carried out in aqueous organic solvent promoted by silver(I) with high anti- and regioselectivity and moderate to good diastereoselectivities. The alkenoyl, cinnamoyl and electron-deficient cinnamoyl substrates smoothly underwent bromohydrin reaction in aqueous acetone but no iodohydrin reaction, where as electron-rich cinnamoyl substrates preferred to undergo iodohydrin reaction in aqueous acetone with moderate diastereoselectivity and enhanced diastereoselectivity was observed in aqueous THF.     

Advantages of the Ns group in the reactions of N-SO2R inosines with benzylamine and with NH3

The reactivity of N¹-alkylsulfonyl- and N¹-arylsulfonyl-2′,3′,5′-tri-O-acetylinosine with benzylamine and with ¹⁵NH₃, regarding the attack on C2, has been shown to be in the order CF₃SO₂ (Tf) > 2,4-(NO₂)₂C₆H₃SO₂ (DNs) ? 4-NO₂C₆H₄SO₂ (pNs) ≈ C₆F₅SO₂ (PFBs) > 2-NO₂C₆H₄SO₂ (Ns) ? CH₃SO₂ (Ms) > 4-CH₃C₆H₄SO₂ (Ts) > 2,4,6-(CH₃)₃C₆H₂SO₂ (Mts). In spite of its intermediate reactivity, the Ns group is the most appropriate, since in this case the formation of by-products is minimised during the ring-opening and ring-closing steps of the process. Another advantage of the Ns group is thus disclosed.     

Site-specific modification of the 5"-terminal fragment of PGY1/MDR1 gene mRNA by reactive conjugates of antisense oligonucleotides

The site-specific modification of the 5"-terminal fragment of PGY1/MDR1 mRNA by oligodeoxyribonucleotide conjugates bearing residues of bleomycin A₅ (Blm), cobalt(ii) tetracarboxyphthalocyanine (Phcn), 4-[N-(2-chloroethyl)-N-methylamino]benzylamine (RCl), or perfluoroarylazide (Az) was studied. Conjugates of oligonucleotides complementary to the RNA sequences 123—138 and 155—166 selectively modify RNA in the vicinity of these regions. The highest efficacy (up to 50%) was achieved in reactions with alkylating and perfluoroarylazide conjugates of oligonucleotides. Conjugates of perfluoroarylazide with 2"-O-modified oligonucleotides are much more efficient than analogous conjugates with oligodeoxyribonucleotides (extents of RNA modification are 40—50% and 20%, respectively).