bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nomenclature of Lignans and Neolignans (IUPAC Recommendations 2000)
Authors: Moss G. P. 
Published: October 2007

Abstract
Lignans and neolignans are a large group of natural products characterized by the coupling of two C6C3 units. For nomenclature purposes the C6C3 unit is treated as propylbenzene and numbered from 1 to 6 in the ring, starting from the propyl group, and with the propyl group numbered from 7 to 9, starting from the benzene ring. With the second C6C3 unit the numbers are primed. When the two C6C3 units are linked by a bond between positions 8 and 8' the compound is referred to and named as a lignan. In the absence of the C-8 to C-8' bond, and where the two C6C3 units are linked by a carbon–carbon bond it is referred to and named as a neolignan. The linkage with neolignans may include C-8 or C-8'. Where there are no direct carbon–carbon bonds between the C6C3 units and they are linked by an ether oxygen atom the compound is named as an oxyneolignan. The nomenclature provides for the naming of additional rings and other modifications following standard organic nomenclature procedures for naming natural products. Provision is included to name the higher homologues. The sesquineolignans have three C6C3 units, and dineolignans have four C6C3 units.
Spontaneous fission half-lives for ground-state nuclide (Technical report)
Authors: Holden Norman E. , Hoffman Darleane C. 
Published: October 2007

Abstract
Measurements of the spontaneous fission half-lives of nuclides of elements Z = 82 through 109 have been compiled (cutoff date of April 1998) and evaluated. Recommended values are tabulated along with total half-lives.
Determination of polar compounds, polymerized and oxidized triacylglycerols, and diacylglycerols in oils and fats: results of collaborative studies and the standardized method (Technical report)
Authors: Dobarganes M. C. , Velasco J. , Dieffenbacher A. 
Published: October 2007

Abstract
A description is given of the development by collaborative study of two standardized methods for the determination of polar compounds in oils and fats by adsorption chromatography using silica minicolumns, and for quantification of polymerized triacylglycerols, oxidized triacylglycerols, and diacylglycerols in polar compounds by high-performance size-exclusion chromatography. The first procedure is sensitive, allowing savings in time, solvents, and reagents as compared to the previous determination (Standard Method 2.507), while the second is very rapid, giving a detailed information on the main groups of compounds in fats and oils associated with hydrolysis, oxidation, and thermal polymerization. Both methods are useful for the analysis of used frying fats as well as for the analysis of virgin or refined oils.
Formylation of carbohydrates and the evolution of synthetic routes to artificial oligosaccharides and glycoconjugates
Authors: Dondoni Alessandro 
Published: October 2007

Abstract
A highly effective method for the synthesis of formyl C-glycosides is described via addition of 2-lithiothiazole or 2-lithiobenzothiazole to sugar lactones, deoxygenation of the resulting ketols, and releasing of the formyl group from the heterocyclic ring. The synthetic utility of these sugar aldehydes is demonstrated by the development of synthetic methods to more elaborate C-glycosides. These include various (1-6)-C-disaccharides and some higher oligomers up to a C,C,C,C-pentasaccharide; C-glycosyl amino acid isosteres of N-glycosyl asparagines; the methylene isostere of β-Δ-galactosyl ceramide; linear and cylic (2-1)-ketoside oligomers. An alternative synthesis of ethylene-bridged glycosyl asparagine isosteres is illustrated by the use of ethynyl C-glycosides as starting materials.
Glyoxylic acid derivatives in asymmetric synthesis
Authors: Jurczak Janusz , Bauer Tomasz 
Published: October 2007

Abstract
Synthesis of chiral derivatives of glyoxylic acid with special emphasis on N-glyoxyloyl-(2R)-bornane-10,2-sultam is presented. Investigation of glyoxylic acid chiral derivatives in various stereocontrolled organic syntheses showed their excellent ability to provide products of high optical purity. Application of our methodology to the synthesis of natural products and their analogs is presented.
Application of directed evolution in the development of enantioselective enzymes
Authors: Reetz Manfred T. 
Published: October 2007

Abstract
A novel approach to developing enantioselective enzymes for use in organic chemistry has been devised which is independent of structural or mechanistic aspects. The underlying idea is to combine appropriate methods of random mutagenesis, gene expression, and high-throughput screening for enantioselectivity. If these actions are performed in repetitive cycles, an evolutionary pressure is created that leads to sequential improvements of the enantioselectivity of a given enzyme-catalyzed reaction. The concept is illustrated by an example involving the lipase-catalyzed hydrolytic kinetic resolution of an α-chiral ester, the enantio-selectivity increasing from ee = 2% (E =1.1) for a wild-type enzyme to ee = 90-93% (E = 25) for the best mutants.
Allylic boron and zinc derivatives in synthesis and transformations of nitrogen heterocycles
Authors: Bubnov Yu. N. , Klimkina E. V. , Zhun' I. V. , Pastukhov F. V. , Yampolsky I. V. 
Published: October 2007

Abstract
Reductive allylation of certain nitrogen heterocycles (indoles, isoquinoline, 4-vinylpyridine, and lactams) with allylic boron and zinc derivatives is presented.
Vinylogous aldol reaction of heterocyclic silyloxy dienes. Application in synthesis
Authors: Casiraghi Giovanni , Zanardi Franca , Rassu Gloria 
Published: October 2007

Abstract
A versatile, readily accessible triad of 2-enoxy silane synthons derived from furan, pyrrole, and thiophene is presented. These heterocycles, in reacting with carbonyl and carbonyl-related acceptors, act as vinylogous nucleophile modules, giving rise to diverse, functionality-rich, γ-substituted α,β-unsaturated carbonyl constructs. These, in turn, are invaluable platforms onto which further functional elements and chirality may be introduced. A couple of appealing applications—the variable construction of a repertoire of carbasugars and a library of annonaceous acetogenin segments—have been chosen to illustrate the viability of this vinylogous aldol approach.
Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, P. R. China
Authors: Ma Shengming , Li Lintao , Wei Qi , Xie Hexin , Wang Guangwei , Shi Zhangjie , Zhang Junliang 
Published: October 2007

Abstract
The hydrohalogenation reactions of electron-deficient allenes, such as 1,2-allenyl ketones, carboxylic acids, esters, amides, nitriles, sulfoxides, sulfones, and phosphine oxides with MX in HOAc, CF3COOH-HOAc, CF3COOH or AlCl3/H2O, afforded β-halo-β,γ-unsaturated functionalized alkenes. The regioselectivity of the reaction could be controlled by the reaction conditions.
Bicyclopropylidene. A unique tetrasubstituted alkene and versatile C6-building block for organic synthesis
Authors: Molander Gary A. 
Published: October 2007

Abstract
Bicyclopropylidene (4), now readily available in preparatively viable quantities, is evolving as a useful C6 building block for organic synthesis due to its enhanced reactivity at the C-H, the C=C, as well as both types of C-C single bonds. Monosubstituted derivatives are accessible by deprotonation/electrophilic substitution. Di- and tetrasubstituted bicyclopropylidenes are best made by copper-mediated reductive dimerization of bromolithiocarbenoids. The 1,3-dipolar cycloadducts of nitrones rearrange to spirocyclopropanated piperidones, palladium-catalyzed codimerizations with acrylates occur with opening of one of the rings to yield precursors to bicyclo[3.3.0]octene and bicyclo[5.3.0]decene skeletons. Silicon-heteroatom bonds can be added across the double bond of 4 under palladium catalysisjust like across a C텡C triple bond, and carbopalladation of the double bond in 4 occurs more rapidly than that in an acrylate. A variety of new three-component reactions of 4 with alkenyl as well as aryl halides and dienophiles have been developed and extended to be carried out in a combinatorial sense, even on a polymer support, with an additional dimension added in the cleavage step. Most of the reported reactions of bicyclopropylidene (4) proceed with good to excellent yields.
Versatility of β-lactams in synthesis. Studies directed toward the synthesis of complex nucleoside antibiotics and some macrocyclic peptides
Authors: Palomo Claudio , Aizpurua Jesús M. , Ganboa Iñaki , Oiarbide Mikel 
Published: October 2007

Abstract
The diastereoselective [2+2] cycloaddition of α-hydroxyketene equivalents with chiral α,ω-oxyaldehyde-derived imines followed by the 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-promoted ring expansion of the resulting α-hydroxy β-lactam adducts provides an unconventional and short route to α-amino acid N-carboxy anhydrides (NCAs). The required enantiopure α,ω-oxyaldehydes were obtained either from the chiral pool or through the Sharpless AD methodology. Following the present strategy, several nonproteinogenic NCAs were synthesized, which were further coupled with α-amino acid esters giving rise to key fragments of some nucleoside antibiotics and macrocyclic peptides.
From phosphatriafulvenes to phosphabenzenes and stable six-membered phosphaallenes
Authors: Hofmann Michael A. , Bergsträßer Uwe , Regitz Manfred 
Published: October 2007

Abstract
Phosphatriafulvenes readily react with kinetically stabilized phosphaalkynes. Depending on the substituent at the phosphorus atom of the phosphatriafulvene, different six-membered phosphaheterocycles can be isolated. On the one hand, 1,3-diphosphabenzenes are formed, which can be isomerized thermally to diphospha dewarbenzenes or complexed by Cr(CO)3. On the other hand, 1,3-diphosphaisobenzenes are thus available. They are converted to bicyclic six-membered allenes via 1,3-dipolar cycloaddition to the P/C double bond.
Use of visible light. Second-generation titanium oxide photocatalysts prepared by the application of an advanced metal ion-implantation method
Authors: Anpo Masakazu 
Published: October 2007

Abstract
Titanium oxide catalysts were implanted with various transition-metal ions by a high-voltage acceleration technique, then calcined in O2 at around 723 K to produce photocatalysts capable of absorbing visible light, the extent of the red shift depending on the amount and kind of metal ions implanted. Such metal ion-implanted titanium oxide photocatalysts, specifically using Cr or V ions, were successful in carrying out various photocatalytic reactions such as the decomposition of NO into N2, O2, and N2O at 293 K, significantly under irradiation with visible light longer than 450 nm. In outdoor field tests, these Cr and V ion-implanted titanium oxide photocatalysts showed three to four times higher photocatalytic reactivity for the decomposition of NO under solar beam irradiation, as compared with the original unimplanted titanium oxide photocatalyst.
Selective monomethylation reactions of methylene-active compounds with dimethylcarbonate. An example of clean synthesis
Authors: Tundo Pietro 
Published: October 2007

Abstract
Dimethylcarbonate (DMC), an environmentally friendly substitute for dimethylsulfate and methyl halides in methylation reactions, is also a very selective reagent. Under batch conditions, with potassium carbonate as the catalyst, the reactions of DMC, used as the solvent of the reactions, with methylene-active compounds (arylacetonitriles and arylacetoesters, aroxyacetonitriles and methyl aroxyacetates, benzylaryl- and alkylaryl-sulfones) produce monomethylated derivatives, with a selectivity not previously observed (i. e., >99%). These are examples of "green chemistry".
Role of reference materials for the realization of physicochemical properties. Past, present, and future
Authors: Marsh Kenneth N. 
Published: October 2007

Abstract
Reference materials have long been considered essential for both calibration and checking the correct operation of equipment used for the determination of physicochemical properties. Up until the 1970s, the maintenance of pure reference materials and the means to verify their properties through measurement using state-of-the-art equipment was the prerogative of many national standards laboratories. Over the last 30 years, many of the standards laboratories have either limited or eliminated their activity in maintaining both reference materials and state-of-the-art measuring equipment. One reason is the ready availability of high-purity materials from commercial sources and the ease with which one can now determine purity. A second reason is the ready availability of instruments to measure digitally fundamental quantities such as time, temperature, length, frequency, and voltage accurately has enabled chemical calibration using reference materials to be replaced in many instruments by electrical calibration. At the same time, digitization has enabled the computerization of the whole measurement process. Such automated devices, if not checked with reference materials, can give highly reproducible results but have large systematic errors, leading to poor values. The role of physicochemical reference materials in the past and the present will be outlined, and their status in the future will be explored.
Endothermic microbial growth. A calorimetric investigation of an extreme case of entropy-driven microbial growth
Authors: von Stockar U. , Marison I. W. , Liu J.-S. 
Published: October 2007

Abstract
Life is almost always associated with the generation of heat. Thus far, all chemotrophic life forms that have been studied in calorimeters were found to be exothermic. Certain literature reports have even cast doubt on the existence of endothermic growth, even though thermodynamic principles do not rule it out. The present report describes the first experiments demonstrating the actual existence of chemotrophic life forms that take up heat rather than produce it.
Potentiometric Selectivity Coefficients of Ion-Selective Electrodes. Part I. Inorganic Cations (Technical Report)
Authors: Umezawa Yoshio , Bühlmann Philippe , Umezawa Kayoko , Tohda Koji , Amemiya Shigeru 
Published: October 2007

Abstract
Potentiometric selectivity coefficients have been collected for ionophore-based ion-selective electrodes (ISEs) for inorganic cations reported from 1988-1997. In addition to numerical values of K
(A,B)
pot together with the methods and conditions for their determination, response slopes, linear concentration ranges, chemical compositions, and ionophores structures for the ISE membranes are tabulated.
Temperature control modes in thermal analysis
Authors: Ozawa Takeo 
Published: October 2007

Abstract
Now we can use several temperature control modes, for example, isothermal run including stepwise heating and cooling, constant rate heating (or cooling), temperature control for sample thermal history, sample-controlled thermal analysis (SCTA or controlled-rate thermal analysis, CRTA), temperature jump, rate jump, temperature modulation, and repeated temperature scanning. Their advantages and drawbacks are reviewed with some illustrative examples, especially for application to kinetic analysis. The combined use of these varieties of temperature control mode is recommended by showing examples. Temperature modulation and repeated temperature scanning are discussed in comparison with temperature-modulated differential scanning calorimetry (DSC), and common and analogous points are elucidated. In relation to this, the possibility of the imaginary part of the overall reaction rate constant in complex reactions is postulated. Finally, these modes are classified and tabulated from two viewpoints, and other possible modes are shown.
Development and application of very high temperature mass spectrometry. Vapor pressure determinations over liquid refractories
Authors: Hastie J. W. , Bonnell D. W. , Schenck P. K. 
Published: October 2007

Abstract
Existing thermodynamic and vaporization data for liquid refractories are based either on estimates or on data extrapolated from studies on the solids obtained at much lower temperatures. Previously, we have shown that pulsed laser heating, coupled with time-dependent mass spectrometry of the free-expansion vapor plume, can be used for semi-quantitative measurements of vaporization thermochemistry. The present work extends this approach with the development of (a) more direct, and more accurate, methods for determining the system temperature and pressure; (b) improved experimental and theoretical determinations of key parameters such as ionization cross sections; and (c) improved characterization of the gas dynamic expansion and thermal equilibration processes. Example material systems considered include C, SiC, Al2O3, ZrO2—7%Y2O3, and Y2O3 at temperatures and total pressures typically in the range of 3000 to 5000 K and 0.01 to 10 bar, respectively (1 bar = 105 Nm-2).
Recent advances in spin chemistry
Authors: Buchachenko Anatoly L. 
Published: October 2007

Abstract
The great success in controlling chemical reactivity by spin manipulation was achieved in the last decade, and many remarkable spin and magnetic phenomena have been discovered. Among those discoveries, the most chemically important highlights are magnetic isotope effect, spin catalysis, and single-spin tunneling spectroscopy. This paper summarizes recent advances in these new and hot areas of modern chemistry.
Influence of chloride, water, and organic solvents on the physical properties of ionic liquids
Authors: Seddon Kenneth R. , Stark Annegret , Torres María-José 
Published: October 2007

Abstract
We report here the first systematic study of the effect of impurities and additives (e.g., water, chloride, and cosolvents) on the physical properties of room-temperature ionic liquids. Remarkably, it was discovered that the viscosity of mixtures was dependent mainly on the mole fraction of added molecular solvents and only to a lesser extent upon their identity, allowing viscosity changes during the course of a reaction to be entirely predictable. While the addition of such molecular solvents decreases the viscosity and density, chloride impurities, arising from the preparation of the ionic liquids, increase viscosity dramatically. The commonly used methods of preparation were validated with respect to chloride impurity.
Reactive intermediates. Some chemistry of quinone methides
Authors: Chiang Y. , Kresge A. J. , Zhu Y. 
Published: October 2007

Abstract
Quinone methides were produced in aqueous solution by photochemical dehydration of o-hydroxybenzyl alcohols (o-HOC6H4CHROH; R = H, C6H5, 4-CH3OC6H4), and flash photolytic techniques were used to examine their rehydration back to starting substrate as well as their interaction with bromide and thiocyanate ions. These reactions are acid-catalyzed and show inverse isotope effects (kH+/kD+ < 1), indicating that they occur through preequilibrium protonation of the quinone methide on its carbonyl carbon atom followed by rate-determining capture of the benzyl carbocations so formed by H2O, Br-, or SCN-. With some quinone methides (R = C6H5 and 4-CH3OC6H4) this acid catalysis could be saturated, and analysis of the data obtained in the region of saturation for the example with R = 4-CH3OC6H4 produced both the equilibrium constant for the substrate protonation step and the rate constant for the rate-determining step. Energy relationships comparing the quinone methides with their benzyl alcohol precursors are derived.
Comparative chemistry of unsaturated compounds of Group 14 elements
Authors: Kira Mitsuo 
Published: October 2007

Abstract
Structures and reactions of a stable dialkylsilylene and various cyclic and acyclic disilenes, which we have recently synthesized, are discussed in detail. The stable silylene was found to be well protected sterically from dimerization but least perturbed electronically as evidenced by UV­vis and NMR spectroscopy. Persilylated acyclic and cyclic disilenes have shown interesting features in the Si=Si bond distances, electronic spectra, and reactions, due to the remarkable electronic and steric effects of trialkylsilyl substituents. Detailed theoretical calculations for the addition of water to disilene has shown that the intramolecular anti-addition pathway is rationalized using the orbital symmetry rule. The reactions of disilenes with haloalkanes were judged to proceed via the rate-determining halogen abstraction of disilenes from haloalkanes. The biradical character of disilenes may be related to the small π bond energy.
Dendrimers as reactive modules for the synthesis of new structure-controlled, higher-complexity megamers
Authors: Tomalia Donald A. , Uppuluri Srinivas , Swanson Douglas R. , Li Jing 
Published: October 2007

Abstract
Dendrimers are macromolecular, nanoscale objects that are widely recognized as precise, mathematically defined, covalent core-shell assemblies. As such, they are composed of quantized numbers of atoms, monomers, and terminal functional groups relative to the respective shell levels (generations) surrounding their cores. Dendrimers have been referred to as molecular-level analogs of atoms. This perspective arises from their potential to function as precise macromolecular tectons (modules), suitable for the synthesis of structure-controlled complexity beyond dendrimers. We have termed this major new class of generic structures "megamers". Our group has now synthesized such "megamer complexity" in the form of both covalent and supra-macromolecular dendri-catenanes, dendri-macrocycles, dendri-clefts, and dendri-clusters. The covalent dendri-cluster subset of megamers has been coined "core-shell tecto(dendrimers)". New mathematically defined, covalent bonding rules for tecto(dendrimer) formation are consistent with sterically induced stoichiometry (SIS) predictions and have been verified experimentally.
In situ speciation measurements. Using diffusive gradients in thin films (DGT) to determine inorganically and organically complexed metals
Authors: Zhang Hao , Davison William 
Published: October 2007

Abstract
The possibilities of using diffusive gradients in thin films (DGT) and anodic stripping voltammetry (ASV) to perform speciation measurements in natural waters are discussed. Both techniques measure labile species, but different approaches have been used to discriminate organic (Corg) and inorganic (Cinorg) metal complexes. In DGT, metals are bound to a resin after passing through a hydrogel that serves as a well-defined diffusion layer. DGT devices with different hydrogels that impede the diffusion of humic substances by different amounts were deployed in solutions of copper and humic substances. Devices with a gel composition that greatly restricted the diffusion of humic substances, but only retarded the diffusion of Cu ions slightly, could be used directly to determine Cinorg. By using different, more open pored gels, which allowed some passage of humic substances, it was possible to determine both Corg and Cinorg. The two separate measurements of Cinorg obtained using the two DGT approaches agreed well. At the high concentrations of Cu used there was good agreement with the predicted distribution from the speciation code WHAM. At the lowest Cu concentration, the proportion of Cinorg estimated using DGT was higher than with WHAM. Possibilities of errors in the DGT or modeling approaches are discussed.