Total Synthesis of Several 3, 3"-Biflavones

BiflavonesareamorecomPlicatedclass0fflavonoids.MostofthemareusefulcomPonentsoftraditionalmedicinetocurediseases.Sincechamaejasminel,anewtoeofbiflavonoidpossessingaC-3/C-3"linkage,wasisolatedfromSteUerachamaejasmaeL.byHuangetal',especiallyafterthebiologicalactivityofani-cancerwasdiscovered',thestUdyof3,3"-biflavonoidshasattfactCdmuchattention.3-5ButtherehasbeennoprogressmentionedonthesynthesisofthiskindofcomPoundsinrecentdecades.AsaresultofoursystematicresearchonthesynthesisofchamaejasInin…     

Synthesis of novel O,O"-dialkyl α-aminoalkylphosphonothioates

O,O"-Dialkyl -amino(cyclohexyl)phosphonothioates were synthesized by the reactions of O,O"-dialkyl phosphonothioites with [2-(N-cyclohexylideneamino)ethyl] vinyl ether.     

γ-Alumina: The Essential and Unexpected Role of Water for the Structure, Stability, and Reactivity of "Defect" Sites

Combining experiments and DFT calculations, we show that tricoordinate Al(III) Lewis acid sites, which are present as metastable species exclusively on the major (110) termination of γ- and δ-Al(2)O(3) particles, correspond to the "defect" sites, which are held responsible for the unique properties of "activated" (thermally pretreated) alumina. These "defects" are, in fact, largely responsible for the adsorption of N(2) and the splitting of CH(4) and H(2). In contrast, five-coordinate Al surface sites of the minor (100) termination cannot account for the observed reactivity. The Al(III) sites, which are formed upon partial dehydroxylation of the surface (the optimal pretreatment temperature being 700 °C for all probes), can coordinate N(2) selectively. In combination with specific O atoms, they form extremely reactive Al,O Lewis acid-base pairs that trigger the low-temperature heterolytic splitting of CH(4) and H(2) to yield Al-CH(3) and Al-H species, respectively. H(2) is found overall more reactive than CH(4) because of its higher acidity, hence it also reacts on four-coordinate sites of the (110) termination. Water has the dual role of stabilizing the (110) termination and modifying (often increasing) both the Lewis acidity of the aluminum and the basicity of nearby oxygens, hence the high reactivity of partially dehyxdroxylated alumina surfaces. In addition, we demonstrate that the presence of water enhances the acidity of certain four-coordinate Al atoms, which leads to strong coordination of the CO molecule with a spectroscopic signature similar to that on Al(III) sites, thus showing the limits of this widely used probe for the acidity of oxides. Overall, the dual role of water translates into optimal water coverage, and this probably explains why in many catalyst preparations, optimal pretreatment temperatures are typically observed in the "activation" step of alumina.     

Nature of "hydrogen bond" in the diborane-benzene complex: covalent, electrostatic, or dispersive?

Motivated by the recent discovery of unusual "hydrogen bonding"-like interaction between a borane system and benzene molecules in a molecular crystal, we carried out quantum mechanical calculations on a model complex, diborane-benzene cluster. The aim is to understand the nature of this unique interaction, which is expected to play an essential role in this novel class of molecular crystals. As analyzed in the present study, the interaction between diborane and benzene is special in the following aspects: (1) this interaction is mostly dispersive; (2) the observed pseudodirectionality with one of the diborane bridge hydrogen directed toward the benzene centroid minimizes the van der Waals contact; and (3) in the "hydrogen bond" map, this interaction is located in a unique region, which is presently populated by a few known molecular complexes with very different chemical characteristics. It is anticipated that the results from the present analysis will provide meaningful guidance for molecular engineering with diborane-benzene as a building block and for stabilization of this and possible other hydrogen bonds by dispersive contributions.     

Special Issue of "Biopolymers"

Biopolymers have more and more important relations with human life.The research on biopolymers involves such fields as chemistry,biology and medicine.In term of source,the biopolymers comprise natural biopolymers and synthetic biopolymers.The development of synthetic biopolymers,especially biodegradable polymers,has enriched the structure,properties and varieties of biopolymers,promoted their applications in many areas such as sutures,bone fixation parts,temporary supporting tubes,drug controlled release carriers and tissue engineering scaffolds.     

Pigment identification on "Pietà" of Barletta, example of Renaissance Apulian sculpture: a Raman microscopy study

A study of the original painting layer of the "Pietà" of Barletta, a polychrome statue, important example of Renaissance Apulian sculpture, was performed by mu-Raman spectroscopy. Vermilion was identified in the original layer of the blood drops on Jesus knee. Lazurite was identified as the original blue pigment on Our Lady's veil and lace, currently a yellow ochre-like color. The use of lazurite demonstrates the historical-artistic importance of this polychrome statue, and supports the hypothesis that this artwork was probably commissioned by Our Lady's devotees to itinerant artists inspired by the more precious Vesperbilder model.     

"Handbook of Organic Chemistry"

本书由Dean,J.A.编著,由McGraw—Hill在1987年出版。它以表格形式按英文字母顺序给出了4000种有机化合物及与有机化学相关的无机化合物的名称、结构式、分子量、Beilstein文献、密度、折光指数、熔点、沸点、闪点和溶解度。其中一部分还给出了物理性质(包括粘度、介电常数、偶极矩和表面张力)、     

Synthesis of esters of α-chloroacetoxy-β,β,β,-trichloroethylphosphonic acids

Summary The synthesis of 11 previously unreported dialkyl esters of -mono-, -di-, and -trichloroacetoxy-,,-trichloroethylphosphonic acids has been effected.     

Cyclization of α-furylmethyl derivatives of linalool by "activated" DMSO

The cyclization of two stereoisomeric -furylmethyl derivatives of linalool initiated by "activated" DMSO leads to the corresponding substituted limonene in low yield. The stereochemistry of these products was not established.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, B-334. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 471–473, February, 1992.     

"Tables of Spectral Data for Structure Determination of Organic Compounds"

《有机化合物结构确定用光谱数据表》第2版(英文)由德国施普林格出版社于1989年出版。该书以表格和框图的形式给出了大量化合物的~(13)C-核磁共振波谱、红外光谱、质谱及电子激发光谱数据,为有机化合物结构的确定提供了重要依据。可供有机化学分析化学专业人员参考。本书已由世界图书出版公司购得重印权,将在     

Electrochemical oxidation of tetramethyl esters of α,α,ω,ω-alcaneteracarboxylic acids

Cyclization of esters of butane-1,1,4,4- and pentane-1,1,5,5-tetracarboxylic acids during electrolysis in methanol in the presence of Nal produces, with a yield of 95%, the esters of cyclobutane-1,1,2,2- and cyclopentane-1,1,2,2-tetracarboxylic acids. Under similar conditions, esters of the highest ,,,-alkanetetracarboxylic acids undergo iodation and hydroxymethylation due to electrical oxidation of methanol to formaldehyde. During electrolysis in methanol in the presence of NaOAc, the esters of ,,,-alkanetetracarboxylic acids undergo effective hydroxymethylation, followed by cyclization into substituted five- and six-member lactones, or tetrahydrofurans when structurally possible.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2332–2339, October, 1992.     

Catalytic, asymmetric, "interrupted" Feist-Bénary reactions

Pyrimidine derivatives of the cinchona alkaloids function as excellent asymmetric catalysts for the "Interrupted" Feist-Bénary Reaction. This reaction produces highly substituted hydroxydihydrofurans from simple starting materials under mild conditions. The asymmetric reaction gives high enantioselectivities with unsubstituted bromoketones, and high enantio- and diastereoselectivities with substituted substrates. Mechanistic experiments suggest that the hydrobromide salt of the alkaloid derivative is the active catalyst for the reaction.     

Structure and energy study of β-diketonates. XV. Composition of superheated vapors and structure of monomeric molecules of <Emphasis Type="Italic">tris</Emphasis>-hexafluoroacetylacetonates of dysprosium,holmium, erbium,and ytterbium

The molecular structure of tris-hexafluoroacetylacetonates of dysprosium, holmium, erbium, and ytterbium (M(hfa)₃, M = Dy, Ho, Er, Yb) is studied in the framework of synchronous electron diffraction and massspectrometric experiment and also quantum-chemically. For all M(hfa)₃ complexes structural parameters r _a , r _g , and r _h1 are found. It is established that the coordination polyhedron LnO₆ has a configuration of D ₃ symmetry. In experiments on superheated vapors of Dy(hfa)₃, Ho(hfa)₃, and Yb(hfa)₃ the molecular forms present in the vapor at different degrees of superheat are determined.