bluuebunny/crossref_metadata_2025 huggingface dataset:
Lycopene and prostate cancer risk. Methodological considerations in the epidemiologic literature
Authors: Giovannucci Edward
Published: October 2007

Prostate cancer is the most common cancer in U.S. males. Among potentially beneficial natural compounds is lycopene, which is derived largely from tomato-based products. Recent epidemiologic studies have suggested a potential benefit of this carotenoid against risk of prostate cancer, but not all of the studies have been supportive. The largest prospective dietary study, the Health Professionals Follow-Up Study (HPFS), had found that 2-4 servings of tomato sauce per week were associated with about a 35 % risk reduction of total prostate cancer and a 50 % reduction of advanced prostate cancer in follow-up from 1986 to 1992. Tomato sauce was by far the strongest predictor of plasma lycopene levels in this study. In the largest plasma-based study, high lycopene levels were associated with similar risk reductions for total and advanced prostate cancer. Results from other studies, mostly dietary case-control studies, have been mixed. The reasons for these inconsistencies are unclear. Because lycopene may come from a number of sources, and the bioavailability of lycopene may vary profoundly across these sources, dietary questionnaires are likely to vary markedly in their utility to estimate true variation in body lycopene stores across individuals. With further follow-up in the HPFS, we addressed some possibilities for apparently conflicting results. We confirmed our initial findings with the independent 1992­1998 follow-up period. Our results also indicated various factors may contribute to some of the inconsistencies, including insufficient sample size, low intake of lycopene, failure to account for bioavailability, reliance on a single dietary assessment, and heterogeneity of prostate cancer.
Carotenoids and cervical, breast, ovarian, and colorectal cancer. Epidemiology and clinical trials
Authors: Rock Cheryl L.
Published: October 2007

Recent observational studies and clinical trials that have investigated the relationship between carotenoids (or diets rich in these compounds) and cervical, breast, ovarian, and colorectal cancer have increased knowledge in this area. Although epidemiological studies suggest a protective association, five randomized controlled trials testing the effect of beta-carotene supplementation on regression of cervical dysplasia, a preneoplastic lesion, did not find an effect on rate of regression. In the Women's Healthy Eating and Living (WHEL) Study, the effects of a high-vegetable carotenoid-rich diet on disease-free survival following treatment for breast cancer is being examined in a randomized multicenter diet intervention trial. Few epidemiological studies of dietary factors and risk for ovarian cancer have been conducted, with mixed results. Early case-control and cohort studies of colorectal cancer have generally suggested a protective effect of vegetable consumption, although a recent large cohort study did not confirm this relationship. In two randomized trials, beta-carotene supplementation was not observed to reduce risk of adenoma recurrence. The Polyp Prevention Trial (PPT), which tested the effect of prescribing increased fruit, vegetable, and fiber intake, and reduced dietary fat, revealed no effect of these efforts on adenoma recurrence in the intent to treat analysis. However, serum carotenoid concentrations were associated with decreased risk of recurrence in that study. To move this area of study forward, more research on mechanisms, surrogate biomarkers, and diet­gene interactions is needed.
Nanostructured advanced materials. Perspectives and directions
Authors: Jortner Joshua , Rao C. N. R.
Published: October 2007

A focus of frontline interdisciplinary research today is the development of the conceptual framework and the experimental background of the science of nanostructured materials and the perspectives of its technological applications. We consider some current directions in the preparation, characterization, manipulation, and interrogation of nanomaterials, in conjunction with the modeling of the unique structure­dynamics­function relations of nanostructures and their assemblies. The implications of quantum size and shape effects on the energetics, nuclear­electronic level structure, electric-optical response and dynamics, reveal new unique physical phenomena that qualitatively differ from those of the bulk matter and provide avenues for the control of the function of nanostructures. Current applications in the realm of nanoelectronics, nanooptoelectronics, and information nanoprocessing are addressed, and other directions highlighted. Chemical sciences make a central contribution to this novel and exciting scientific­technological area.
Synthesis of monodispersed model catalysts using softlanding cluster deposition
Authors: Abbet Stéphane , Judai Ken , Klinger Laurent , Heiz Ueli
Published: October 2007

In nanocatalysis, clusters deposited on solid, well-defined surfaces play an important role. For the detection of size effects it is, however, important to prepare samples consisting of deposited clusters of a single size, as their chemical properties change with the exact number of atoms in the cluster. In this paper, the experimental tools are presented to prepare such model systems. The existence of monodispersed clusters is confirmed by various experimental findings. First, the carbonyl formation of deposited Nin clusters shows no change in the nuclearity when comparing the size of the deposited clusters with one of the formed carbonyls. Second, scanning tunneling microscopy (STM) studies show that fragmentation of Sin clusters upon deposition can be excluded. In addition, the adsorption behavior of CO on deposited Pd atoms points to the existence of single atoms on the surface. Furthermore, CO oxidation results on Aun clusters confirm the existence of monodispersed clusters trapped on well-defined adsorption sites. Finally, we use Monte-Carlo simulations to define the range of clusters and defect densities, for which monodispersed clusters can be expected.
Nanophase materials by a novel microwave-hydrothermal process
Authors: Komarneni Sridhar , Katsuki Hiroaki
Published: October 2007

While there are many techniques for the production of nanophase materials, we have been using a hydrothermal process because it is a low-temperature method that can lead to energy savings. A recent innovation is the introduction of microwaves in the hydrothermal system, and we named this process the microwave-hydrothermal (M-H) process. M-H synthesis is a novel processing technology for the production of a variety of nanophase ceramic oxide and metal powders under closed-system conditions. This closed-system technology not only prevents pollution at its source, but also saves energy and, thus, could substantially reduce the cost of producing nanophase powders of all kinds. With several examples, the value of this technique is reviewed here. The M-H technique leads to (a) rapid heating to temperature of treatment, which can save energy and time; (b) increased reaction kinetics by one to two orders of magnitude, which also saves time and energy; (c) formation of novel phases; and (d) selective crystallization.
Morphology of nanostructured materials
Authors: Sanyal M. K. , Datta A. , Hazra S.
Published: October 2007

Here we shall discuss the importance of grazing incidence X-ray scattering techniques in studying morphology of nanostructured materials confined in thin films and multilayers. In these studies, the shapes, sizes, and structures of nanostructured materials and their distribution in composites are investigated. These studies are important for understanding properties that may deviate considerably from the known bulk properties. We shall first outline basics of three X-ray scattering techniques, namely X-ray reflectivity, grazing incidence small-angle X-ray scattering, and grazing incidence diffraction, used for these studies. We shall then demonstrate the utility of these techniques using some known results.
Self-assembled molecular films of tetraamino metal (Co, Cu, Fe) phthalocyanines on gold and silver. Electrochemical and spectroscopic characterization
Authors: Somashekarappa M. P. , Keshavayya J. , Sampath S.
Published: October 2007

The formation of molecular films of 2,9,16,23-tetraamino metal phthalocyanines [TAM(II)Pc; M (II) = Co, Cu, and TAM(III)Pc; M = Fe] by spontaneous adsorption on gold and silver surfaces is described. The properties of these films have been investigated by cyclic voltammetry, impedance, and FT-Raman spectroscopy. The charge associated with Co(II) and Co(I) redox couple in voltammetric data leads to a coverage of (0.35 ± 0.05) x 10-10 mol cm-2, suggesting that the tetraamino cobalt phthalocyanine is adsorbed as a monolayer with an almost complete coverage. The blocking behavior of the films toward oxygen and Fe(CN)6
3-/4- redox couple have been followed by cyclic voltammetry and impedance measurements. This leads to an estimate of the coverage of about 85% in the case of copper and the iron analogs. FT-Raman studies show characteristic bands around 236 cm-1 revealing the interaction between the metal substrate and the nitrogen of the -NH2 group on the phthalocyanine molecules.
Formation of interfacial phases in the epitaxial growth of Sb on Si(111)-7 ¥ 7 reconstructed surface
Authors: Paliwal Vinod Kumar , Vedeshwar A. G. , Shivaprasad S. M.
Published: October 2007

Understanding the evolution of the Sb/Si(111) interface is of great interest in the formation of devices of nanodimensions. We have undertaken in situ (∼10-11 torr) studies of Sb adsorption (at room temperature) and its desorption on the 7 X 7 reconstructed Si(111) surface, by complementary techniques such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and electron energy loss spectroscopy (EELS). For room-temperature (RT) Sb adsorption, the overlayer grows in the Frank van der Merwe mode, forming an interface state of δ(7 X 7) in the submonolayer Sb coverage regime. Adsorption of 1.0 monolayer (ML) Sb at RT shows an abrupt shift of 0.8 eV in the peak position of the Sb 3d5/2 transition owing to band-bending caused by a metallic (7 X 7) to a semiconducting (1 X 1) surface phase transformation. Changes observed in full width at half-maximum (fwhm) and Sb 3d3/2 and 3d5/2 branching ratio are discussed. Thermal annealing experiments provide evidence for agglomeration of Sb islands, before the multilayer and monolayer desorption. During this desorption process, we have observed two novel surface phases of (5 X 5) at 0.4 ML and (5√3 X 5√3­R30°) at 0.2 ML, stable at higher temperatures.
Some properties of spherical and rod-shaped semiconductor and metal nanocrystals
Authors: Landes Christy F. , Link Stephan , Mohamed Mona B. , Nikoobakht Babak , El-Sayed Mostafa A.
Published: October 2007

In this paper, we summarize our results on the effect of changing size and shape of semiconductor and metallic nanocrystals. The change in size (from 3.5 to 1.1 nm) and shape (from spherical to rod) of CdSe nanocrystals is found to affect both their optical and nonradiative properties. In gold quasi-spherical nanocrystals, results on the dependence of the electron-phonon relaxation of the surrounding medium are presented. For gold nanorods, results and conclusions on the mechanism of their self-assembly are presented. Enhanced Raman scattering on their surfaces is studied and compared with that on spherical particle surfaces.
Photoinduced transformations in semiconductor­metal nanocomposite assemblies
Authors: Kamat Prashant V.
Published: October 2007

Semiconductor­metal nanocomposites provide a simple and convenient way to tailor the properties of photocatalysts. Modification of semiconductor surface improves charge separation and promotes interfacial charge-transfer processes in nanocomposite systems. Charge accumulation in the metal layer results in Fermi-level equilibration raising the quasi-Fermi level of the composite close to the conduction band level of the oxide semiconductor. Phototransformations of such compositesincluding morphological changes, interfacial charge-transfer processes and photocurrent generation of TiO2-capped gold colloidsare presented in this review article.
Photochemistry of chromophore-functionalized gold nanoparticles
Authors: Thomas K. George , Ipe Binil Itty , Sudeep P. K.
Published: October 2007

It is generally believed that metal nanoparticles strongly quench the singlet-excited states of chromophores when attached to nanoparticle surfaces, through an energy-transfer mechanism, which limits their application in optoelectronic devices and photonic materials. Recent studies of fluorophore-linked metal nanoparticles reveal that there is a dramatic suppression in the quenching of the singlet-excited state of these molecules and they possess unusual photophysical properties. A summary of our work on the photophysical and excited-state properties of chromophore-functionalized gold nanoparticles is presented in this article. Pyrene-capped gold nanoparticles showed normal fluorescence in nonpolar solvents and an intermolecular excimer formation at higher loadings. The quenching of the emission, observed in pyrene-labeled gold nanoparticles in polar solvents, is attributed to the formation of pyrene radical cation through a photoinduced electron-transfer process. We have also functionalized gold nanoparticles using a thiol derivative of fullerene. The quenching of fluorescence and decreased yields of triplet-excited state, observed in these systems, are attributed to an energy-transfer process.
Functional nanoparticle architectures for sensoric, optoelectronic, and bioelectronic applications
Authors: Willner Itamar , Willner Bilha
Published: October 2007

Tailored sensoric, electronic, photoelectrochemical, and bioelectrocatalytic functions can be designed by organized molecular or biomolecular nanoparticle hybrid configurations on surfaces. Layered receptor-cross-linked Au nanoparticle assemblies on electrodes act as specific sensors of tunable sensitivities. Layered DNA-cross-linked CdS nanoparticles on electrode supports reveal organized assemblies of controlled electronic and photoelectrochemical properties. Au nanoparticle-FAD semisynthetic cofactor units are reconstituted into apo-glucose oxidase (GOx) and assembled onto electrodes. The resulting enzymes reveal effective electrical contacting with the electrodes, and exhibit bioelectrocatalytic functions toward the oxidation of glucose to gluconic acid. Magneto-switchable electrocatalysis and bioelectrocatalysis are accomplished by the surface modification of magnetic particles with redox-relay units. By the attraction of the modified magnetic particles to the electrode support, or their retraction from the electrode, by means of an external magnet, the electrochemical functions of the magnetic particle-tethered relays can be switched between "ON" and "OFF" states, respectively. The magneto-switchable redox functionalities of the modified particles activate electrocatalytic transformations, such as a biocatalytic chemoluminescence cascade that leads to magneto-switchable light emission or the activation of bioelectrocatalytic processes.
Sea-water solubility phase diagram. Application to an extractive process
Authors: Cohen-Adad R. , Balarew Chr. , Tepavitcharova S. , Rabadjieva D.
Published: October 2007

The main goal of this presentation is to tentatively forecast or improve an extractive process. The sea-water system is described using a graphical representation of the quinary ion-pair system Na+, K+, Mg2+/Cl−, SO4
2-//H2O. The operations required by extraction or purification of a sea-water component are simulated by a path through the solubility diagram.The procedure is applied to isothermal evaporation of Black Sea water at 25 °C, and the balance of the crystallization sequence is determined. In the same way, the cooling of residual brine, after precipitation of pure sodium chloride, is studied.
Predicting bioconcentration factors of highly hydrophobic chemicals. Effects of molecular size
Authors: Dimitrov S. D. , Dimitrova N. C. , Walker J. D. , Veith G. D. , Mekenyan O. G.
Published: October 2007

The bioconcentration factor (BCF) is a parameter that describes the ability of chemicals to concentrate in aquatic organisms. Traditionally, it is modeled by the log–log quantitative structure -activity relationship (QSAR) between the BCF and the octanol- water partition coefficient (Kow). A significant scatter in the parabolic log(BCF)/log(K
ow) curve has been observed for narcotics with log(K
ow) greater than 5.5. This study shows that the scatter in the log(BCF)/log(K
ow) relationship for highly hydrophobic chemicals can be explained by the molecular size. The significance of the maximal cross-sectional diameter on bioconcentration was compared with the traditionally accepted effective diameter. A threshold value of about 1.5 nm for this parameter has been found to discriminate chemicals with log(BCF) > 3.3 from those with log(BCF) < 3.3. This critical value for the maximum diameter is comparable with the architecture of the cell membrane. This threshold is half thickness of leaflet constituting the lipid bilayer. The existence of a size threshold governing bioconcentration is an indication of a possible switch in the uptake mechanism from passive diffusion to facilitated diffusion or active transport. The value of the transition point can be used as an additional parameter to hydrophobicity for predicting BCF variation. The effect of molecular size on bioconcentration has been studied by accounting for conformational flexibility of molecules.
Solubility equilibria. From data optimization to process simulation
Authors: Königsberger Erich
Published: October 2007

Models that accurately predict solid–solute phase equilibria in aqueous electrolyte solutions are of mounting importance for numerous industrial processes, especially those operating at high temperatures, pressures, and concentrations. The incorporation of such electrolyte models into process simulators is in great demand. This communication will focus on thermodynamically consistent models that can simultaneously predict densities, heat capacities, and apparent molar enthalpies of multicomponent electrolyte mixtures together with activities of their constituents. Data optimization issues to be discussed include the CALPHAD (CALculation of PHAse Diagrams) method applied to electrolyte systems and the generation of robust models that extrapolate well outside the parameterization space. Recent development of software suitable for the simulation of industrial processes involving concentrated electrolyte solutions will be outlined.
Arsenic. An environmental problem limited by solubility
Authors: Magalhães M. Clara F.
Published: October 2007

Arsenic is a toxic element for animals and the majority of plants, in spite of evidence that it is also an essential element. The long-term intake of small doses of arsenic has a carcinogenic effect. There are well-identified regions where arsenic ground water concen- trations can reach values higher than 2 mg/L. Water purification and waste treatment techniques based on (1) precipitation of calcium, magnesium, and iron(III) arsenates, and/or (2) adsorption or coprecipitation of arsenic oxyanions are unlikely to produce aqueous solutions with arsenic concentrations below the guideline values proposed for arsenic dissolved in potable water and treated sewage effluents. As(III) species are more toxic than As(V) species. Arsenate species are predominant at moderate and high redox potentials, while arsenite species occur under more reducing conditions. Metal arsenites are much more soluble than the corresponding metal arsenates, and arsenites are adsorbed less by solid phases. Remediation techniques must consider the available information on solubility and adsorptive properties of As(III) and As(V). The less-soluble lead and barium arsenates are not suitable for arsenic decontamination. New remediation methods must consider solubility data for arsenic-containing materials and minerals.
Cation order/disorder in lithium transition-metal oxides as insertion electrodes for lithium-ion batteries
Authors: Zhecheva E. , Stoyanova R. , Alcántara R. , Lavela P. , Tirado J.-L.
Published: October 2007

Results on the local cation ordering in layered lithium-nickel/cobalt oxides and metal-substituted lithium-manganese spinels are presented. It is shown that electron spin resonance of Ni3+ and Mn4+ and magnetic susceptibility measurements are powerful tools to monitor the short-range cation ordering in these compounds, which is not accessible by diffraction techniques. Thus, owing to the different strength of the 90° and 180° Ni3+–O–Ni3+/2+ exchange interactions, the distribution of Ni3+/Ni2+ between the lithium and nickel layers in Li1–x
Ni1+x
O2 with 0 < x < 0.4 can be determined. For layered LiNi1–y
Co
y
O2 and spinel LiMn2–x
Co
x
O4 solid solutions, analysis of the temperature-independent EPR line width in terms of dipole–dipole and exchange interactions has been used to examine the local Ni3+/Co3+ and Mn4+/Co3+ ordering. The results obtained are correlated with the electrochemical intercalation of lithium in these compounds.
Aquatic chemistry and solubility phenomena of actinide oxides/hydroxides
Authors: Fanghänel Thomas , Neck V.
Published: October 2007

The present paper gives an overview of the solubility behavior of actinide oxides/hydroxides, taking into account hydrolysis reactions up to colloid formation. The analogies, systematic trends, and differences in the hydrolysis and solubility constants of actinides in the oxidation states An(III) to An(VI) correlate with the charge and size of the actinide ions. The formation of amorphous and crystalline solids and the discrepancies between the corresponding experimental solubility data may be explained as an effect of particle size. However, using thermodynamic data for the stable crystalline solids, the predicted solubilities are often significantly lower than experimental data (even in long-time experiments), indicating that the solubility is controlled by the surface properties. Typical examples are the known U(VI) solids schoepite and sodium diuranate. The most striking example is provided by the tetravalent actinides. Above the threshold of hydrolysis, the dissolution of microcrystalline or crystalline An(IV) oxides is found to be irreversible. The measured concentrations approach those of the amorphous hydroxides or hydrous oxides.
Solid–liquid equilibria in mixtures of molten salt hydrates for the design of heat storage materials
Authors: Voigt W. , Zeng D.
Published: October 2007

Enthalpy of melting can be used to store heat in a simple way for time periods of hours and days. Knowledge of the solid –liquid equilibria represents the most important presumption for systematic evaluations of the suitability of hydrated salt mixtures. In this paper, two approaches for predicting solid–liquid equilibria in ternary or higher component systems are discussed using the limited amount of thermodynamic data available for such systems. One method is based on the modified Brunauer–Emmett–Teller (BET) model as formulated by Ally and Braunstein.

In cases of a strong tendency toward complex formation of salt components, the BET model is no longer applicable. Reaction chain models have been used to treat such systems. Thereby, the reaction chain represents a method to correlate step-wise hydration or complexation enthalpies and entropies and, thus, reduce the number of adjustable parameters. Results are discussed for systems containing MgCl2, CaCl2, ZnCl2, and alkali metal chlorides.
Isotope-abundance variations of selected elements (IUPAC Technical Report)
Authors: Coplen Tyler B. , Böhlke John Karl , De Bièvre P. , Ding T. , Holden N. E. , Hopple J. A. , Krouse H. R. , Lamberty A. , Peiser H. S. , Revesz K. , Rieder S. E. , Rosman K. J. R. , Roth E. , Taylor P. D. P. , Vocke R. D. , Xiao Y. K.
Published: October 2007

Documented variations in the isotopic compositions of some chemical elements are responsible for expanded uncertainties in the standard atomic weights published by the Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry. This report summarizes reported variations in the isotopic compositions of 20 elements that are due to physical and chemical fractionation processes (not due to radioactive decay) and their effects on the standard atomic-weight uncertainties. For 11 of those elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, copper, and selenium), standard atomic-weight uncertainties have been assigned values that are substantially larger than analytical uncertainties because of common isotope-abundance variations in materials of natural terrestrial origin. For 2 elements (chromium and thallium), recently reported isotope-abundance variations potentially are large enough to result in future expansion of their atomic-weight uncertainties. For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium, and tellurium), documented isotope variations in materials of natural ter- restrial origin are too small to have a significant effect on their standard atomic-weight uncertainties. This compilation indicates the extent to which the atomic weight of an element in a given material may differ from the standard atomic weight of the element. For most elements given above, data are graphically illustrated by a diagram in which the materials are specified in the ordinate and the compositional ranges are plotted along the abscissa in scales of (1) atomic weight, (2) mole fraction of a selected isotope, and (3) delta value of a selected isotope ratio.
Hierarchical transfer of stereochemical information in synthetic macromolecules
Authors: Cornelissen J. J. L. M.
Published: October 2007

In Nature, a wide variety of complex tasks (e.g., catalysis, transport, and information storage) is performed by biomacromolecules with precise composition, dimensions, and architecture. To achieve the precise organization required for efficient function, structural information is built into the smallest building blocks of biomacromolecules (i.e., amino and nucleic acids) and subsequently transferred in a hierarchical fashion to form larger quaternary structures. These construction principles have been an inspiration for synthetic and supramolecular chemists alike, and a number of synthetic biomimetic helical macromolecules have been reported in the recent literature. Here, some recent developments in the field of helical polyisocyanides will be reviewed in combination with new prospects on the self-organization of protein/polymer hybrid architectures.
Assemblies of conjugated polymers: Intermolecular and intramolecular effects on the photophysical properties of conjugated polymers
Authors: Kim Jinsang
Published: October 2007

Conjugated polymers are emerging materials for electronic applications due to the tunability of their properties through variation of their chemical structure. Their applications, which currently include light-emitting diodes (LEDs), field effect transistors (FETs), plastic lasers, batteries, and sensors, are expanding to many new areas. The two critical parameters that determine the function of conjugated polymer-based devices are chemical structure and nanostructure of a conjugated polymer in the solid state. While the physical properties of isolated polymers are primarily controlled by their chemical structure, these properties are drastically altered in the solid state due to electronic coupling between polymer chains as determined by their interpolymer packing and conformation. However, the development of effective and precise methods for controlling the nanostructure of polymers in the solid state has been limited because polymers often fail to assemble into organized structures due to their amorphous character and large molecular weight.

In this review, recent developments of organizing methods of conjugated polymers and the conformation and interpolymer interaction effects on the photophysical properties of conjugated polymers are summarized.
Aromatic core-modified expanded porphyrinoids with meso-aryl substitutents
Authors: Pushpan S. K. , Chandrashekar T. K.
Published: October 2007

Porphyrins are the most widespread of all prosthetic groups found in Nature. The ubiquity of their functions in Nature led researchers around the globe to focus their attention on these highly colored macrocycles. The interdisciplinary interest generated by porphyrins resulted in the syntheses of modified porphyrins, which can be put to a variety of uses in medicine and industry. A brief overview of the synthetic methodologies resulting in the formation of aromatic meso-aryl-substituted core-modified aromatic heterocyclic ring-inserted expanded porphyrinoids like sapphyrins, smaragdyrins, rubyrins, hexaphyrins, heptaphyrins, and octaphyrins reported to date are discussed in this article.
Use of the term "recovery" and "apparent recovery" in analytical procedures (IUPAC Recommendations 2002)
Authors: Burns D. T. , Danzer Klaus , Townshend A.
Published: October 2007

The terms recovery and apparent recovery are recommended to avoid confusion caused by the use of the term recovery to cover two distinct situations. These situations deal with: (a) the yield of a preconcentration or extraction stage of an analytical process (where recovery is recommended) and (b) the quantity observed value/reference value, obtained using an analytical procedure that involves a calibration graph (where apparent recovery is recommended).
Critical evaluation of stability constants of phosphonic acids (IUPAC Technical Report)
Authors: Popov Konstantin , Rönkkömäki Hannu , Lajunen Lauri H. J.
Published: October 2007

The following reference citations were incorrect:

Page 1643: replace 93SC with 93SK

Page 1657: replace H+: 98KK with H+: 98KA

Page 1657: replace Cu2+: 98KK with Cu2+: 98KA

Page 1668: replace 90S with 90SW

Page 1673: replace 68BE with 67BE

Page 1666: replace 95WJ J.M. Wagener and N.V. Jarvis. S. Afr. J. Chem. 28, 85 (1995) with 95WJ J.M. Wagener and N.V. Jarvis. S. Afr. J. Chem. 48, 85 (1995)

Page 1666: replace 95I with 95IU

Page 1668: replace 90K A T. Kiss with 90KA T. Kiss
Chemical crop protection research. Methods and challenges
Authors: Müller U.
Published: October 2007

Chemical crop protection, today a well-established technology to support sustainable production of food, feed, and fiber, will continue to play an important role in agribusiness in spite of the emergence of novel biotechnological solutions. Scientific progress in chemistry, biology, and molecular biology has revolutionized the way of searching for new agrochemicals over the past decade. Requirements, primarily in terms of safety to humans and the environment, have also changed. The search for and the development of novel agrochemicals with novel modes of action, improved safety profiles, and adapted to the changing requirement of the food and feed production chain are more than ever the challenge.
Advances in biocatalytic synthesis. Enzyme-triggered asymmetric cascade reactions
Authors: Glueck S. M. , Mayer S. F. , Kroutil Wolfgang , Faber K.
Published: October 2007

Organic compounds can be transformed through enzyme-triggered domino (or cascade) reactions via several (inseparable) consecutive steps in an asymmetric fashion to yield nonracemic products. Despite the fact that these sequences often involve the occurrence of highly reactive unstable intermediates, the overall efficiency of these processes can be high, provided that the reaction rates of the individual steps match each other in order to minimize side reactions.
Synthetic studies on the marine natural product halichondrins
Authors: Choi Hyeong-wook , Demeke Damtew , Kang F.-A. , Kishi Y. , Nakajima K. , Nowak P. , Wan Z.-K. , Xie C.
Published: October 2007

In connection with the de elopment of a practical synthesis of the right half, and its analog E7389, of halichondrin B, an efficient and scalable synthesis of the two major building blocks is reported. In addition, a new synthesis of the C20–C26 segment via a regiospecific and stereoselecti e SN2' process is presented. A sulfonamide class of ligands is shown to be effective for asymmetric Ni/Cr-mediated reactions under both stoichiometric and catalytic conditions, and the X-ray structure reveals this class of ligands to be tridentate. On the basis of three X-ray structures, a possible mechanism is suggested for this process. Stable and crystalline Cr(III)/sulfonamide complexes are shown to be effective for catalytic Cr-mediated coupling reactions of allyl, alkenyl, and alkyl halides with aldehydes, and some examples for application of the stoichiometric and catalytic asymmetric processes are presented.
Synthesis of azaheterocycles from oxime derivatives
Authors: Narasaka K.
Published: October 2007

Electrophilic amination of Grignard reagents has been accomplished by using O-sulfonyloximes as amination reagents. Benzophenone O-sulfonyloxime derivatives react with Grignard reagents on sp2 nitrogen, yielding primary amines by successive hydrolysis of the resulting N-alkylimines.

Various cyclic imines are synthesized by Pd-catalyzed reaction from olefinic oxime derivatives. That is, treatment of O-pentafluorobenzoyloximes of olefinic ketones with a catalytic amount of Pd(PPh3)4 and triethylamine affords nitrogen-containing heterocycles, such as pyrroles, pyridines, isoquinolines, spiro-imines, and aza-azulenes. This reaction proceeds via the initial formation of alkylideneaminopalladium(II) species generated by oxidative addition of the oximes to the Pd(0) complex, and the following intramolecular amination on the olefinic moiety.

Cyclic imines are prepared from γ,δ-unsaturated O-acetyloximes by treatment with acetic acid and 1,4-cyclohexadiene in the presence of a catalytic amount of 1,5-naphthalene-diol. γ,δ-Unsaturated ketone O-methoxycarbonyloximes are transformed to 2-bromomethyl-3,4 dihydro-2H-pyrroles by the action of a catalytic amount of Cu(I) bromide dimethyl sulfide complex and lithium bromide.
Stereocontrolled total synthesis of (+)-vinblastine
Authors: Yokoshima Satoshi , Ueda T. , Kobayashi S. , Sato A. , Kuboyama Takeshi , Tokuyama H. , Fukuyama T.
Published: October 2007

Stereocontrolled total synthesis of (+)-vinblastine (1) has been achieved using a novel radical-mediated indole synthesis developed in our laboratories. The isothiocyanate 18, prepared readily from quinoline 17, underwent a facile addition of the malonate anion to give 19. The o-alkenylthioanilide 19 was then converted to indole 20 by radical cyclization and protection. (−)-Vindoline (2) was prepared from this key intermediate 20 in a highly efficient manner. The indole core of the 11-membered intermediate 3 was constructed similarly from quinoline. The critical coupling reaction between 2 and the chloroindolenine derived from 3 proceeded with complete control of stereochemistry to give the desired product 66 in 97 % yield, which could be successfully converted to (+)-vinblastine (1).
Applications of tert-butanesulfinamide in the asymmetric synthesis of amines
Authors: Ellman J. A.
Published: October 2007

tert-Butanesulfinamide is prepared using catalytic enantioselective methods in two steps from the extremely inexpensive oil waste by-product, tert-butyl disulfide. Direct condensation of tert-butanesulfinamide with aldehydes and ketones provides tert-butanesulfinyl imines in uniformly high yields. The tert-butanesulfinyl group activates the imines for the addition of many different classes of nucleophiles, serves as a powerful chiral directing group, and after nucleophilic addition is readily cleaved by treatment with acid. A wide range of highly enantioenriched amines, including α-branched and α,α-dibranched amines, α- and β-amino acids, 1,2 and 1,3-amino alcohols and α-trifluoromethyl amines are efficiently synthesized using this methodology.
Application of cascade processes toward heterocyclic synthesis
Authors: Padwa A.
Published: October 2007

The reactions ofN-acyliminium ions with tethered π-bonds are among the most important methods for preparing complex nitrogen-containing heterocycles. Pummerer-based cyclizations are also finding widespread application in both carbo- and heterocyclic syntheses. As part of a program concerned with new methods for alkaloid synthesis, we became interested in using a linked Pummerer/N-acyliminium ion cyclization sequence since we felt that this combination offers unique opportunities for the assemblage of complex target molecules. A synthetic method that combines transformations of different reaction types significantly broadens the scope of such procedures in synthetic chemistry. α-Thiocarbocations generated from the Pummerer reaction of β-phenylsulfinylmethyl-α,β-unsaturated amides can be intercepted by the adjacent amido group to produce transient amino- substituted furans, which undergo subsequent Diels-Alder cycloadditions. Using thisdomino amido-Pummerer/Diels-Alder cascade, we were able to assemble novel polycyclic systems in a single operation. The key step in the process involves the generation of a reactiveN-acyliminium ion by fragmentation of an amino-substituted [4+2] cycloadduct. The successful synthesis of a number of alkaloids by this sequence of reactions reveals the usefulness and importance of this unique domino cascade.
Unified strategy for the synthesis of C-aryl glycosides
Authors: Martin S. F.
Published: October 2007

A unified approach for the synthesis of the four major groups of C-aryl glycosides has been developed. The strategy incorporates two integrated approaches, the first of which features the [4+2] cycloaddition of a glycosyl furan with a substituted benzyne followed by the acid-catalyzed opening of the resultant adduct. The second route involves the sequential palladium-catalyzed opening of a benzyne-furan cycloadduct with an iodo glycal followed by oxidation of the resultant dihydronaphthol ring and reduction of the glycal moiety. The utility of this strategy has been established by a concise formal synthesis of the C-aryl glycoside antibiotic galtamycinone.
Critical evaluation of stability constants and thermodynamic functions of metal complexes of crown ethers (IUPAC Technical Report)
Authors: Arnaud-Neu Francoise , Delgado Rita , Chaves Sílvia
Published: October 2007

Stability constants and thermodynamic functions of metal complexes of crown ethers in various solvents published between 1971 and the beginning of 2000 have been critically evaluated. The most studied crown ethers have been selected: 1,4,7,10 tetraoxacyclododecane (12C4), 1,4,7,10,13 pentaoxacyclopentadecane (15C5), and 1,4,7,10,13,16 hexaoxacyclooctadecane (18C6). The metal ions chosen are: alkali and alkaline earth metal ions, Ag+, Tl+, Cd2+, and Pb2+. The solvents considered are: water, methanol, ethanol, and their mixtures, as well as acetonitrile, N,N'-dimethylformamide, dimethylsulfoxide, and propylene carbonate. The published data have been examined and grouped into two categories, “accepted” and “rejected”. The “accepted” values were considered as: (i) recommended (R), when the standard deviations (s.d.) on the constant K or on Δr
H were inferior to 0.05 lg unit or inferior to 1 kJ mol−1, respectively; (ii) provisional (P), when s.d. is superior to 0.05 and inferior to 0.2 for lg K or s.d. is superior to 1 and inferior to 2 kJ mol−1 for Δr
H; (iii) recommended 1 (R1), if the values were obtained by a single research group, but were considered reliable in comparison with related systems, and considering that the research team usually presents R-level values for other similar systems.
Critical evaluation of the chemical properties of the transactinide elements (IUPAC Technical Report)
Authors: Kratz J. V.
Published: October 2007

In this paper, the chemical properties of the transactinide elements rutherfordium, Rf (element 104); dubnium, Db (element 105); and seaborgium, Sg (element 106) are critically reviewed. The experimental methods for performing rapid chemical separations on a time scale of seconds are reviewed, and comments are given on the special situation with the transactinides for which the chemistry has to be studied with single atoms. There follows a systematic description of theoretical predictions and experimental results on the chemistry of Rf, Db, and Sg - their mutual comparison and evaluation. The literature cited has the cutoff date of March 1999. The more recent chemical identification of bohrium, Bh (element 107), and of hassium, Hs (element 108), should be evaluated in a future Part II of this report.
Inspirations from nature. New reactions, new therapeutic leads, and new drug delivery systems
Authors: Wender P. A. , Baryza J. L. , Brenner S. E. , Clarke M. O. , Gamber Gabriel G. , Horan J. C. , Jessop T. C. , Kan Cindy , Pattabiraman K. , Williams T. J.
Published: October 2007

Studies in our laboratory focus on problems in chemistry (new reactions and synthesis), biology (novel modes of action), and medicine (new therapeutic leads and drug delivery systems). These interconnected and often synergistic activities are inspired by an interest in novel structures, frequently from nature, that possess unique modes of action and significant clinical potential. Described herein are some examples of recent work from our laboratory that have led to new transition metal-catalyzed reactions, a new and remarkably potent therapeutic lead, and new drug delivery systems that are in clinical trials.
Antiangiogenic heparin-derived heparan sulfate mimics
Authors: Casu Benito , Naggi A.
Published: October 2007

Heparan sulfate (HS) is a glycosaminoglycan (GAG) widely distributed as a proteoglycan on the cell surface and in the extracellular matrix of animal tissues. Among other important physiological functions, its polysaccharide chains mediate cell proliferation by binding growth factors [fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF)], which are released in active form through the action of the enzyme heparanase overexpressed by tumor cells. HS is constituted of alternating disaccharide sequences of variously sulfated uronic acid (d-glucuronic, GlcA, or l-iduronic, IdoA) and glucosamine (N-acetylated, GlcNAc, or N-sulfated, GlcNSO3). HS mimics can be obtained by chemical modification of heparin, a more highly sulfated GAG clinically used as an anticoagulant and antithrombotic drug. With the aim of obtaining antagonists of FGFs as potential inhibitors of tumor neo-vascularization (angiogenesis), arrays of short FGF-binding sequences have been obtained by generating sulfation gaps within the prevalent (IdoA2SO3–GlcNSO36SO3)
n
sequences of heparin, by controlled base-catalyzed removal of 2-O-sulfate groups of IdoA2SO3 residues.The C(2)–C(3) bond of all nonsulfated uronic acid residues have then been split with periodate, to generate flexible joints along the polysaccharide chain. The novel heparin derivative (poly-PST.sU), chiefly made up of the repeating tetrasaccharide units –GlcNSO36SO3– IdoA2SO3– GlcNSO36SO3– sU– (where sU is a glycol-split and reduced uronic acid residue) binds FGF2 as strongly as heparin. However, it is a poor inducer of formation of FGF2 dimers and of complexes with FGF receptors, required for triggering mitogenic signals. NMR and molecular modeling studies indicate that formation of these higher-order complexes is prevented by the unfavorable conformation induced by glycol-split residues. In a parallel study, partially N-acetylated heparins have been obtained that efficiently inhibit heparanase upon glycol-splitting. It is noteworthy that glycol-splitting involves inactivation of the active site for antithrombin, with consequent loss of anticoagulant activity. In contrast, poly-PST.sU and some of its analogs show potent antiangiogenic activity in in vivo models in which heparin is either proangiogenic or inactive.
Semisynthesis and degradation of the tubulin inhibitors epothilone and tubulysin
Authors: Höfle G. , Glaser N. , Leibold T. , Karama U. , Sasse F. , Steinmetz H.
Published: October 2007

The structure-activity relationships of epothilones indicate that major modifications are only tolerated in the western ring segment. In particular, C2 methyl of the thiazole ring appears to be most flexible. Its broad modification started from epothilone F, which was obtained from natural epothilone B by hydroxylation via the N-oxide. Some of the prepared derivatives exhibit improved esterase stability in addition to high cytotoxic activity. For these and other favorable properties, amine (BMS-310705) was recently introduced in clinical trials. In an alternative approach, modified side chains were introduced by replacement of the C12,C15 ring segment via ring-opening olefin metathesis (ROM) of epothilone C in the presence of ethylene to 12,13-seco-epothilone C, introduction of a synthetic building block followed by ring-closing olefin metathesis (RCM), and epoxidation to the 16-alkyne analog of epothilone A.

The structure of the tetrapeptide tubulysin D was confirmed by total hydrolysis to N-methyl d-pipecolic acid, l-isoleucine, tubuvaline (Tuv), tubuphenylalanine (Tup), formaldehyde, and 3-methylbutyric acid. Mild acidic hydrolysis to cyclo-tubulysin andoxidative degradation to l-valine allowed the assignment of the stereocenters of Tuv, hydrazinolysis, and comparison with synthetic reference samples to that of Tup. The absolute configuration of tubulysin D is: (R)-Mep, (2,3S)-Ile, (1'R ,3'R)-Tuv, and (2S,4R)-Tup.
Synthesis of carbohydrate-based antibiotics
Authors: Wong C.-H. , Bryan M. C. , Nyffeler P. T. , Liu H. , Chapman Eli
Published: October 2007

Tackling the problem of carbohydrate recognition is a subject of current interest. Our strategies in this regard include development of new methods for the synthesis of saccharides and sugar arrays for screening, design of d-peptides to target bacterial cell-surface sugars, preparation of mechanism-based inhibitors of the enzymes involved in the biosynthesis of saccharides and the synthesis of aminoglycoside mimetics to target RNA.
DNA minor-groove binders. Design, synthesis and biological evaluation of ligands structurally related to CC-1065, distamycin, and anthramycin
Authors: Baraldi P. G. , Tabrizi M. A. , Preti D. , Fruttarolo Francesca , Avitabile Barbara , Bovero Andrea , Pavani G. , del Carretero M. Carmen Nunez , Romagnoli R.
Published: October 2007

Many natural and synthetic anticancer agents with the ability to interact with DNA have been discovered, but most have little sequence-specificity and often exhibit severe toxicity to normal tissues. Thus, there has been considerable interest in molecular biology and human medicine to find small molecules that can alkylate the DNA in a sequence-specific manner and modify the function of nucleic acids irreversibly. Analogs of naturally occurring antitumor agents, such as distamycin A, which bind in the minor groove of DNA, represent a new class of anticancer compounds currently under investigation. Distamycin A has driven researchers' attention not only for its biological activity, but also for its nonintercalative binding to the minor groove of double-stranded B-DNA, where it forms a strong reversible complex preferentially at the nucleotide sequences consisting of 4-5 adjacent adenine-thymine (AT) base pairs. The pyrrole-amide skeleton of distamycin A has been also used as DNA sequence-selective vehicles for the delivery of alkylating functions to DNA targets, leading to a sharp increase of its cytotoxicity, in comparison to that, very weak, of distamycin itself.

In the last few years, several hybrid compounds, in which derivatives of naturally occurring antitumor agents, such as anthramycin or the alkylating unit of the antibiotic CC-1065, have been tethered to distamycin frames. The DNA alkylating and cytotoxic activities against several tumor cell lines are reported and discussed in terms of their structural differences in relation to both the number of N-methyl pyrrole rings and the type of alkylating unit tethered to the oligopeptidic frame.