Synthesis and cytotoxic activity of Boc-protected pentapeptide amide analogs of somatostatin

Russian Chemical Bulletin - New Boc-protected pentapeptide amides of the general formula Boc—Cys(Boc)—Phe—d-Trp—Lys(Boc)—Thr—NHR, which are analogs of the...     

均三嗪含氮取代基衍生物的结构和性质

在B3LYP/aug-cc-pvDZ理论水平上研究了—CN、—NO2、—NH2、—N3 、—N2H、—NHNH2、—N4H和—N4H3等含氮取代基取代均三嗪环上的氢原子生成的衍生物, 预测了它们的分子构型、分解能及含能性质. 对衍生物分解能的研究结果表明, —CN 和—NH2取代的衍生物的分解能比未取代时更高, 而其余基团的取代使分解能降低; 取代基化合物的生成热越大, 取代均三嗪中的氢原子后生成衍生物的生成热也越大. —CN、—N3和—N4H取代的均三嗪衍生物的单位原子生成热为71.9、78.7 和82.6 kJ, 比文献报道的三叠氮基-均三嗪的(70.2 kJ)更高. —N4H、—N3 、—N4 H3 、—N2 H和—CN取代的均三嗪衍生物, 生成热为863.1-1735.2 kJ·mol-1, 但—N4H和—N4H3取代的衍生物分解能较小,稳定性较差.     

Asymmetric Synthesis XV: Enantioselective Syntheses of (R) or (S) —α—Substituted— (2 — Pyridyl) Methylamines Via Chiral Pinanone Ketimine Template

Enantioselective synthesis of (R) or (S)—α—substituted—(2 — pyridyl) — methylamines (5), using 2—hydroxypinan — 3 — one (1) as chiral auxiliary, had been studied. The e. e values of 5 were 89～ 98%, which determined by chiral capillary GC (stationary phase; Chirasil — Val).     

Asymmetric Synthesis XIII: The Stereocontrolled Synthesis of (R)—α—Amino Acids via a Double Chiral Induction

The stereocontrolled synthesis of (R)—α—amino acids via a double chiral induction in alkylation of the ketimine derived from (+)—camphor and (+)—menthyl glycinate which is a chiral match pair has been studied. (R)—α—amino acids wih high optical purity 80–90% are obtained after hydrolysis of the alkylated products. We find that the chiral match which is the symergistic effect in a double chiral induction is very important to abtain the higher diastereoselectivity for the stereocontrolled synthesis.     

新型降血压药物分子K—252a结构相似物的合成

采用直链型缩醛与 N,N—二甲基—邻—苯二胺偶联,合成了一种环状结构和天然降血压药物分子 K—252a相似的新化合物。本文报导了这种新化合物的全台成过程并讨论了一种新的成环反应机理。     

1,4,7,10—四氮杂环十二烷的制备

N,N′,N″—三(对—甲苯磺酰基)二亚乙基三胺与氢化钠反应生成二钠盐,然后与N,O,O'—三(对—甲苯磺酰基)双(2—羟乙基)胺进行缩合环化反应,得N—对甲苯磺酰化的四氮杂环十二烷。在浓H_2SO_4作用下,脱去对—甲苯磺酰基,最后得到了1,4,7,10—四氮杂环十二烷,总得率为44％。     

Phase equilibrium calculations of highly polar systems

It is well known that highly polar and hydrogen bonding mixtures pose a serious challenge to equations of state. In the present report it is shown that excellent correlations and predictions of complex systems can be achieved when the van der Waals mixing rules are properly associated with an equation of state. In this report the proper form of the van der Waals mixing rules is used with the Peng—Robinson equation of state to predict the vapor—liquid equilibrium properties of water—ketone, water—alcohol, alcohol—ketone, and other complex mixtures, which exhibit either positive or negative azeotropy, with an accuracy which was not achievable by the original form of Peng—Robinson equation of state of mixtures.     

聚锆碳硅烷陶瓷先驱体的制备与表征

为了提高SiC陶瓷纤维的综合性能,利用聚二甲基硅烷(PDMS)热解制得的液相产物聚硅碳硅烷(PSCS)与乙酰丙酮锆(Zr(AcAc)4)反应,制备了含锆SiC陶瓷纤维的先驱体聚锆碳硅烷(PZCS).选用液相PSCS作为反应原料,可使锆元素在先驱体中分布更加均匀,并能防止Zr(AcAc)4在反应过程中升华.实验合成的PZCS化学式为SiC1.94HxO0.066Zr0.0104,数均分子量Mn=200~400,再成型性良好.反应机理研究表明,反应过程中存在PSCS裂解重排反应,Si—H键在反应中显示出很高的活性,PZCS分子量的增加是PSCS形成的Si—H键与Zr(AcAc)4的配位基发生交联反应的结果.利用PZCS制备的Si—Zr—C—O陶瓷纤维平均强度2.6GPa,平均直径11μm,性能优异.     

聚砜、聚二甲基硅氧烷、聚对羟基苯乙烯三元多嵌段共聚物的形态结构

利用动态力学分析（ＤＭＡ）．透射电子显微镜（ＴＥＭ）和小角Ｘ 光光散射（ＳＡＸＳ）对聚砜（ＰＳＦ）、聚二甲基硅氧烷（ＰＤＭＳ）和聚对羟基苯乙烯（ＰＨＳ）三元多嵌段共聚物ＰＳＦ—ＰＤＭＳ—ＰＨＳｎ的形态结构进行了研究．结果表明，ＰＳＦ—ＰＤＭＳ—ＰＨＳｎ的形态结构出现了许多新的现象，除具有微相分离的基本特征外，还出现双连续相双分散相的特征．在适当的嵌段长度和组成下，通过ＴＥＭ观察到一种新的特殊形态 蜂窝状形态结构，并在嵌段共聚物两相界面处直接观察到非常清晰的界面相．同时，对该形态的形成过程作了初步讨论．     

Double anomeric effects and a hydrogen‐bonded supramolecular motif in N,N′‐bis(3‐nitrophenyl)methanediamine

In the title compound, C₁₃H₁₂N₄O₄, the molecule lies on a crystallographic twofold axis. Molecules are linked into complex sheets parallel to (100) via one N—H...O and two C—H...O hydrogen bonds. Within the molecule, the 3‐nitroanilino fragment is essentially planar, and the C—N—C—N—C fragment assumes a nearly perpendicular/perpendicular conformation, with C—N—C—N torsion angles of 81.18 (18)°, which is controlled by a pair of adjacent anomeric interactions. The findings constitute the first demonstration of two anomeric effects existing in one N—C—N unit.     

Phosphonium and arsonium ylides. XVII. A facile synthesis of methyl 2,6-bisperfluoroalkylbenzoates via acyclic precursors

The title compounds 6a—6f were prepared with high yield via intramolecular Wittig reaction of methyl 3-perfluoroalkyl-6-peifluoroacyl-2-triphenylphosphoranylidenchex-3,5-dienoates (5a—5i) which were obtained from the reaction of 3-perfluoroacylprop-2-enylidenetriphenylphosphoranes (3a—3c) with methyl perfluoroalkynoates (4a—4c).     

Relations for molecular integrals of relativistic interactions

Relations are derived which connect the molecular integrals of variation of electron mass from relativity, spin—orbit interaction, orbit—orbit interation and spin—spin interaction with the overlap, the nuclear attraction and the electron repulsion integrals.     

吡啶与HCl和CHCl3形成分子间红移氢键和蓝移氢键的理论研究

采用量子化学从头算的MP2方法, 分别在6-31G(d,p), 6-311+G(d,p)和AUG-cc-pVDZ基组下, 研究了复合物C5H5N…HCl(1), C5H5N…HCCl3(2)和C5H5N…HCCl3(3)的分子间氢键. 计算结果表明, 在复合物1中, HCl中Cl—H键伸长, 形成Cl—H…N红移氢键; 在复合物2中, HCCl3中C—H键伸长, 形成C—H…N 红移氢键; 在复合物3中, HCCl3中C—H键收缩, 形成C—H…π蓝移氢键. 自然键轨道(NBO)分析表明, 影响氢键红移和氢键蓝移主要有3个因素: n(Y)→σ*(X—H)超共轭作用、X—H键轨道再杂化和质子供体电子密度重排. 其中, 超共轭作用属于键伸长效应, 电子密度重排和轨道再杂化属于键收缩效应. 在复合物1和2中, 由于键伸长效应处于优势地位导致形成红移氢键; 在复合物3中, 由于键收缩效应处于优势地位导致形成蓝移氢键.     

S-亚硝基-N-乙酰基-D,L-青霉胺二肽分子中S—NO键断裂能的测定

利用滴定量热技术并结合适当的热力学循环测定了乙腈溶液中7个S-亚硝基-N-乙酰基-D,L-青霉胺二肽化合物中S—NO键的异裂能和均裂能, 其能量范围分别为234.5—246.2 kJ/mol和101.6—122.1 kJ/mol. 结果表明, 所研究的亚硝基硫醇化合物更容易通过S—NO键的均裂释放NO自由基(NO·). 通过热力学循环对7个亚硝基硫醇化合物自由基负离子中S—NO键的异裂能和均裂能进行估算, 能量范围分别为19.2—35.5 kJ/mol和-4.2—22.6 kJ/mol, 表明这些自由基负离子在室温下不稳定, 容易通过S—NO键的异裂释放出NO-.     

N‐Chloro­acetyl‐β‐alanine

The β‐alanine residue of the title compound, C₅H₈ClNO₃, has a ggt folded conformation, which is mainly stabilized through intermolecular N—H⋯O=C (amide–acid) and O—H⋯O=C (acid–amide) hydrogen bonds. In addition, a cis conformation is found for the Cl—CH₂—C(=O)—NH torsion angle, which is associated with the presence of an intramolecular hydrogen bond.     

An experimental study of three- and four-phase equilibria for isopropanol—water—carbon dioxide mixtures at elevated pressures

Compositions and molar volumes of the three phases in liquid—liquid—gas equilibrium are reported for ternary mixtures of isopropanol, water and CO₂ at elevated pressures and at temperatures of 50 and 60°C. Phase compositions and molar volumes were also obtained for three-phase, liquid—liquid—liquid equilibrium and four-phase, liquid—liquid—liquid—gas equilibrium at 40°C. Gas—liquid and liquid—liquid critical endpoints, which represent pressure bounds on the liquid—liquid—gas region at 60°C, were determined from observations of critical opalescence.The phase behavior exhibited by the isopropanol—water—CO₂ system is quite complex, particularly at conditions near the critical point of CO₂. These conditions are well within the range of operating conditions proposed for supercritical-fluid extraction of organic compounds from water using CO₂. Therefore, the existence of multiple coexisting phases can be an important factor in designing and operating such extraction processes.     

Excess enthalpies of binary and ternary mixtures of acetonitrile with methanol,ethanol and benzene

Excess molar enthalpies are measured for the binary mixtures methanol—acetonitrile and ethanol—acetonitrile at 25 and 35°C and for the ternary mixtures methanol—acetonitrile—benzene and ethanol—acetonitrile—benzene at 25°C using an isothermal dilution calorimeter. The binary results are well reproduced with an association model which contains four equilibrium constants for the association of alcohol, two equilibrium constants for that of acetonitrile, and two solvation equilibrium constants between alcohol and acetonitrile molecules. The ternary results are compared with those calculated from the model with binary parameters.     

硼取代后氨化处理的分子筛碱性的理论研究

利用笼状的分子筛模型, 在B3LYP/6-311++G(d,p)水平下通过对分子筛中各种碱性基团的碱性进行对比来预测硼取代后氨化处理的分子筛的碱性. 结果表明, B-NH2基团本身碱性不强, 但与质子或路易斯酸作用时, B-NH2基团与周围的Si-OH基团共同参与作用并导致碱性增强. 另外, 分子筛中含有的Si-NH2基团也可与周围的B-OH共同作用, 产生强碱性. 因此, 硼取代后氨化处理的分子筛是一种优良的碱性材料.     

An unusual two‐dimensional hydrogen‐bonding network in bis(2,9‐dimethyl‐1,10‐phenanthrolin‐1‐ium) peroxodisulfate dihydrate

The title compound, 2C₁₄H₁₃N₂⁺·S₂O₈²⁻·2H₂O, is a protonated amine salt which is formed from two rather uncommon ionic species, namely a peroxodisulfate (pds²⁻) anion, which lies across a crystallographic inversion centre, and a 2,9‐dimethyl‐1,10‐phenanthrolin‐1‐ium (Hdmph⁺) cation lying in a general position. Each pds²⁻ anion binds to two water molecules through strong water–peroxo O—H...O interactions, giving rise to an unprecedented planar network of hydrogen‐bonded macrocycles which run parallel to (100). The atoms of the large R₈⁸(30) rings are provided by four water molecules bridging in fully extended form (...H—O—H...) and four pds²⁻ anions alternately acting as long (...O—S—O—O—S—O...) and short (...O—S—O...) bridges. The Hdmph⁺ cations, in turn, bind to these units through hydrogen bonds involving their protonated N atoms. In addition, the crystal structure also contains π–π and aromatic–peroxo C—H...O interactions.     

Solvent effects on the vibrational structure of the ultraviolet spectra of cyanoaromatics. The influence of electron—donor—acceptor (EDA) interactions—II. Studies in binary solvent mixtures

The concept of preferential solvation has been used to detect and quantify specific interactions, particularly electron—donor—acceptor (EDA) interactions for the solutes 1-cyanonaphthalene and 1,2-dicyanobenzene which can act as π electron acceptors. These acceptors have been studied in binary solvent mixtures, in which one of the solvents can act as an electron donor while the other is an “inert” cosolvent.Thus we analysed the preferential solvation of the aromatic compounds in the following mixtures: cyclohexane—diethylether, cyclohexane—diethylamine, diethylamine—diethylether, cyclohexane-diisopropylamine, cyclohexane—diisopropylether and diisopropylamine—diisopropylether.The evaluation of the degree of preferential solvation was performed by an analysis of the intensity enhancements of the vibronic absorption spectral bands of the acceptors in the binary mixtures. This method seems to be a useful approach to observing preferential solvation, is proposed as a method to detect EDA interaction, for systems where no new bands are observed such as in complexes between cyanoaromatics and aliphatic amines.