bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ring Opening Reactions ‐ Heterogeneous
Authors: Paál Zoltán 
Published: March 2010

Abstract

The ring opening of cyclopentanes occurs more readily on metal catalysts (Pt, Pd, Ir, Rh, etc.) than hydrogenolysis of open‐chain alkanes because of the hindered free rotation. Different mechanisms proposed are reviewed. The position of ring opening is usually hindered close to the alkyl substituent(s) on metals but favored on acidic catalysts where C5C6 ring enlargement takes place. Product distribution on different metals and bimetallic systems is discussed. Smaller (C3, C4) rings give open‐chain products more readily. Catalyst composition affects the stereochemistry of opening of substituted cyclopropanes. Larger cycles also undergo ring contraction to aromatics, together with the formation of bicyclic products. The practical importance of opening of substituted C
6
cycles to alkanes in upgrading fuel components (rather than their aromatization) is presently increasing. Spirocyclic hydrocarbons also undergo isomerization and subsequent aromatization. Oxacycloalkanes (C3C5 heterocycles containing oxygen) produce alcohols in a hydrogenolytic ring‐opening process or carbonyls with skeletal rearrangement.
Transesterification ‐ Biological
Authors: Kanerva Liisa T. , Liljeblad Arto 
Published: March 2010

AbstractEnzymatic transesterification reactions, mainly alcoholysis and interesterification reactions with hydrolytic enzymes leading to transesterification products as final products, are considered. The main emphasis is on enzymatic kinetic and dynamic kinetic resolution and on regioselective acyl transfers. Brief illustration of factors, such as irreversible acyl donors and reaction media affecting the outcome of biocatalysis as well as consideration of reaction mechanisms, is included.
Immobilization ‐ Biological
Authors: Berberich Jason , Erbeldinger Markus , Sinclair Jessica Jenkins , Walker Jeremy P. 
Published: March 2010

AbstractEnzyme biocatalysts are responsible for many types of reactions. In their natural state, enzymes are very susceptible to destabilization in environments outside physiological conditions. This results in a loss of catalytic activity of the enzyme. Enzymes can be stabilized for use in these environments by immobilization. Immobilization includes both physical entrapment and covalent attachment and results in retention of the enzymes' structure and activity. The authors describe how immobilization of enzymes aids in stabilizing enzymes for use in practical applications.
Two Photon Polymerization‐Micromolding of Polyethylene Glycol‐Gentamicin Sulfate Microneedles
Authors: Gittard Shaun D. , Ovsianikov Aleksandr , Akar Hasan , Chichkov Boris , Monteiro‐Riviere Nancy A. , Stafslien Shane , Chisholm Bret , Shin Chun‐Che , Shih Chun‐Ming , Lin Shing‐Jong , Su Yea‐Yang , Narayan Roger J. 
Published: March 2010

AbstractThe use of microneedles for transdermal drug delivery is limited due to the risk of infection associated with formation of channels through the stratum corneum layer of the epidermis. The risk of infection associated with use of microneedles may be reduced by imparting these devices with antimicrobial properties. In this study, a photopolymerization‐micromolding technique was used to fabricate microneedle arrays from a photosensitive material containing polyethylene glycol 600 diacrylate, gentamicin sulfate, and a photoinitiator. Scanning electron microscopy indicated that the photopolymerization‐micromolding process produced microneedle arrays that exhibited good microneedle‐to‐microneedle uniformity. An agar plating assay revealed that microneedles fabricated with polyethylene glycol 600 diacrylate containing 2 mg mL−1 gentamicin sulfate inhibited growth of Staphylococcus aureus bacteria. Scanning electron microscopy revealed no platelet aggregation on the surfaces of platelet rich plasma‐exposed undoped polyethylene glycol 600 diacrylate microneedles and gentamicin‐doped polyethylene glycol 600 diacrylate microneedles. These efforts will enable wider adoption of microneedles for transdermal delivery of pharmacologic agents.
One‐Pot Three‐Step Synthesis of Naphtho[2,3‐a]carbazole‐ 5,13‐diones using a Tandem Radical Alkylation–Cyclization– Aromatization Reaction Sequence
Authors: Ding Chunyong , Tu Shanghui , Yao Qizheng , Li Fulong , Wang Yuanxiang , Hu Wenxiang , Zhang Ao 
Published: March 2010

AbstractA three‐step, one‐pot tandem reaction including radical nucleophilic alkylation/cyclization/aromatization was developed using 0.3 equivalents of silver(I) acetate (AgOAc) as the catalyst and 2 equivalents of ammonium persulfate [(NH4)2S2O8] as the oxidant. This strategy is highly efficient for the assembly of pentacyclic complex carbazoles from aryl‐fused bromobenzoquinones and indol‐3‐ylpropanoic acid acids in 52–72% overall yields (three steps). This new approach provides a significant improvement over the previously reported methods and would greatly facilitate analog library construction of pentacyclic complex carbazoles and benefit further biological evaluation of these compounds.
Barrier requirements as the evolutionary “driver” of epidermal pigmentation in humans
Authors: Elias Peter M. , Menon Gopinathan , Wetzel Bruce K. , Williams John (Jack) W. 
Published: March 2010

AbstractCurrent explanations for the development of epidermal pigmentation during human evolution are not tenable as stand‐alone hypotheses. Accordingly, we assessed instead whether xeric‐ and UV‐B‐induced stress to the epidermal permeability barrier, critical to survival in a terrestrial environment, could have “driven” the development of epidermal pigmentation. (1) Megadroughts prevailed in central Africa when hominids expanded into open savannahs [≈1.5–0.8 million years ago], resulting in sustained exposure to both extreme aridity and erythemogenic UV‐B, correlating with genetic evidence that pigment developed ≈1.2 million years ago. (2) Pigmented skin is endowed with enhanced permeability barrier function, stratum corneum integrity/cohesion, and a reduced susceptibility to infections. The enhanced function of pigmented skin can be attributed to the lower pH of the outer epidermis, likely due to the persistence of (more‐acidic) melanosomes into the outer epidermis, as well as the conservation of genes associated with eumelanin synthesis and melanosome acidification (e.g., TYR, OCA2 [p protein], SLC24A5, SLC45A2, MATP) in pigmented populations. Five keratinocyte‐derived signals (stem cell factor⇒KIT; FOXn1⇒FGF2; IL‐1α, NGF, and p53) are potential candidates to have stimulated the sequential development of epidermal pigmentation in response to stress to the barrier. We summarize evidence here that epidermal interfollicular pigmentation in early hominids likely evolved in response to stress to the permeability barrier. Am. J. Hum. Biol., 2010. © 2010 Wiley‐Liss, Inc.
Volatile Organic Compound Sensing by Quartz Crystal Microbalances Coated with Nanostructured Macromolecular Metal Complexes
Authors: Kimura M. , Sugawara M. , Sato S. , Fukawa T. , Mihara T. 
Published: March 2010

AbstractWe report the construction of a molecular recognition layer composed of polyelectrolyte brushes and metal complexes on the surface of a quartz crystal microbalance (QCM) and the sensing abilities for various volatile organic compounds (VOCs). Atom‐transfer radical polymerization of 2‐(dimethylamino)ethyl acrylate from an initiator‐terminated self‐assembled monolayer yielded polyelectrolyte brushes on the surface of a weight‐detectable quartz crystal microbalance. One end of a poly[(2‐dimethylamino)ethyl methacrylate] brush was covalently attached onto the surface of a sensor. We found that metallophthalocyanines with four bulky pentaphenylbenzene substituents could adsorb volatile organic compounds selectively into their cavities. Macromolecular metal complexes were prepared by immersing polymer‐brush‐modified QCMs into an aqueous solution of sterically protected cobalt phthalocyanine. Anionic cobalt phthalocyanine was trapped in the polymer brushes and acted as a molecular receptor for the sensing of VOC molecules.
Systematic Evaluation of Substituted Cyclopentadienyl Ruthenium Complexes, [(η5‐C5MenH5−n)RuCl(cod)], for Catalytic Cycloadditions of Diynes
Authors: Yamamoto Yoshihiko , Yamashita Ken , Harada Yu 
Published: March 2010

AbstractA series of η5‐cyclopentadienylruthenium complexes, [(η5‐C5MenH5−n)RuCl(cod)] (cod=1,5‐cyclooctadiene), are evaluated as catalysts for the cycloaddition of 1,6‐diynes with alkynes. As a result, we unexpectedly found that the complex bearing the 1,2,4‐Me3Cp ligand is the most efficient catalyst in terms of turnover number (TON) for the cycloaddition of a bulky diiododiyne with acetylene, recording the highest TON of 970 with a catalyst loading of 0.1 mol %. To obtain insight into this result, we evaluate the electron richness of all complexes by cyclic voltammetric analyses, which indicate that the electron density of the ruthenium center increases with an increase in methyl substitution on the Cp′ ligands. The initial rate (up to 10 % conversion) of the cycloaddition was then measured using 1H NMR spectroscopy. The initial rate is found to decrease as the number of methyl substituents increases. According to these results, we assumed that the optimum catalytic performance exhibited by the 1,2,4‐trimethylcyclopentadienyl complex can be attributed to its robustness under the catalytic cycloaddition conditions. The steric and electronic effects of the Cp′ ligands are also investigated in terms of the regioselectivity of the cycloaddition of an unsymmetrical diyne and in terms of the chemoselectivity in the cycloaddition of a 1,6‐heptadiyne with norbornene.
Structural Investigation of the Binding of 5‐Substituted Swainsonine Analogues to Golgi α‐Mannosidase II
Authors: Kuntz Douglas A. , Nakayama Shinichi , Shea Kayla , Hori Hitoshi , Uto Yoshihiro , Nagasawa Hideko , Rose David. R. 
Published: March 2010

AbstractGolgi α‐mannosidase II (GMII) is a key enzyme in the N‐glycosylation pathway and is a potential target for cancer chemotherapy. The natural product swainsonine is a potent inhibitor of GMII. In this paper we characterize the binding of 5α‐substituted swainsonine analogues to the soluble catalytic domain of Drosophila GMII by X‐ray crystallography. These inhibitors enjoy an advantage over previously reported GMII inhibitors in that they did not significantly decrease the inhibitory potential of the swainsonine head‐group. The phenyl groups of these analogues occupy a portion of the binding site not previously seen to be populated with either substrate analogues or other inhibitors and they form novel hydrophobic interactions. They displace a well‐organized water cluster, but the presence of a C(10) carbonyl allows the reestablishment of important hydrogen bonds. Already approximately tenfold more active against the Golgi enzyme than the lysosomal enzyme, these inhibitors offer the potential of being extended into the N‐acetylglucosamine binding site of GMII for the creation of even more potent and selective GMII inhibitors.
Approaches towards the Efficient Use of Resources in the Industry
Authors: Schmidt M. 
Published: March 2010

AbstractResource efficiency in companies targets economic and efficient use of materials and energy in production. On the one hand, this aims to contribute towards sustainable development and, on the other hand, efficient use of resources can save costs and improve the competitiveness of a company. This aspect is becoming all the more important in the light of current developments in world market prices for natural resources. In Germany, the use of materials and energy currently accounts for about 46 % of the gross value of goods manufactured by companies. It is known from various sources that the average potential for savings here is 10–15 %. The material costs alone can be reduced by 2–3 % through efficient management. The potentials for saving lie less in the individual technologies applied and more in the interplay within and between the complex production systems. That is why one key challenge facing the industry is to ascertain the hidden costs that are in fact linked with inefficiencies in a company. Analysis methods and approaches are necessary for this, such as for example the material and energy flow analysis.
Electron Donor–Acceptor Interactions in Regioselectively Synthesized exTTF2–C70(CF3)10 Dyads
Authors: Takano Yuta , Herranz M. Ángeles , Martín Nazario , de Miguel Rojas Gustavo , Guldi Dirk M. , Kareev Ivan E. , Strauss Steven H. , Boltalina Olga V. , Tsuchiya Takahiro , Akasaka Takeshi 
Published: March 2010

AbstractThe decakis(trifluoromethyl)fullerene C1‐C70(CF3)10, in which the CF3 groups are arranged on a para7‐meta‐para ribbon of C6(CF3)2 edge‐sharing hexagons, and which has now been prepared in quantities of hundreds of milligrams, was reacted under standard Bingel–Hirsch conditions with a bis‐π‐extended tetrathiafulvalene (exTTF) malonate derivative to afford a single exTTF2–C70(CF3)10 regioisomer in 80 % yield based on consumed starting material. The highly soluble hybrid was thoroughly characterized by using 1D 1H, 13C, and 19F NMR, 2D NMR, and UV/Vis spectroscopy; matrix‐assisted laser desorption ionization (MALDI) mass spectrometry; and electrochemistry. The cyclic voltammogram of the exTTF2–C70(CF3)10 dyad revealed an irreversible second reduction process, which is indicative of a typical retro‐Bingel reaction; whereas the usual phenomenon of exTTF inverted potentials (${E{{1\hfill \atop {\rm ox}\hfill}}}$>${E{{2\hfill \atop {\rm ox}\hfill}}}$), resulting in a single, two‐electron oxidation process, was also observed. Steady‐state and time‐resolved photolytic techniques demonstrated that the C1‐C70(CF3)10 singlet excited state is subject to a rapid electron‐transfer quenching. The resulting charge‐separated states were identified by transient absorption spectroscopy, and radical pair lifetimes of the order of 300 ps in toluene were determined. The exTTF2–C70(CF3)10 dyad represents the first example of exploitation of the highly soluble trifluoromethylated fullerenes for the construction of systems able to mimic the photosynthetic process, and is therefore of interest in the search for new materials for photovoltaic applications.
Syntheses of Fumagillin and Ovalicin
Authors: Yamaguchi Junichiro , Hayashi Yujiro 
Published: March 2010

AbstractThis review focuses on the synthetic strategies used for the construction of fumagillin, ovalicin, and other natural products of this family that are known angiogenesis inhibitors. These compounds are comprised of a cyclohexane framework, two epoxides, and five or six contiguous stereogenic centers. The first total syntheses of fumagillin and ovalicin were reported by Corey in 1972 and 1985, respectively. There were numerous studies directed at these natural products in the decades that followed with many reports appearing in the year 2000 or later. Despite the relatively small size of these molecules, their syntheses highlight the efficient construction of stereogenic centers in organic synthesis.
Theoretical Investigations on the Mechanism of Hetero‐Diels–Alder Reactions of Brassard’s Diene and 1, 3‐Butadiene Catalyzed by a Tridentate Schiff Base Titanium(IV) Complex
Authors: Su Zhishan , Qin Song , Hu Changwei , Feng Xiaoming 
Published: March 2010

AbstractThe mechanism of the hetero‐Diels–Alder reactions of Brassard’s diene and 1,3‐butadiene catalyzed by a titanium(IV) complex of a tridentate Schiff base was investigated by DFT and ONIOM methods. The calculations indicate that the mechanism of the reaction is closely related to the nucleophilicity–electrophilicity between diene and carbonyl substrates. A stepwise pathway is adopted for Brassard’s diene, and the step corresponding to the formation of the CC bond is predicted to be the rate‐determining step with a free‐energy barrier of 8.4 kcal mol−1. For 1,3‐butadiene, the reaction takes place along a one‐step, two‐stage pathway with a free‐energy barrier of 14.9 kcal mol−1. For Brassard’s diene as substrate, the OCH3 and OSi(CH3)3 substituents may play a key role in the formation of the transition state and zwitterionic intermediate by participating in charge transfer from Brassard’s diene to formaldehyde. The combination of the phenyl groups at the amino alcohol moiety and the ortho‐tert‐butyl group of the salicylaldehyde moiety in the chiral tridentate Schiff base ligand plays an important role in the control of the stereoselectivity, which is in agreement with experimental observations.
From Nanorods to Atomically Thin Wires of Anatase TiO2: Nonhydrolytic Synthesis and Characterization
Authors: Liu Chenmin , Sun Hui , Yang Shihe 
Published: March 2010

AbstractA nonhydrolytic two‐step chemical process has been developed to synthesize ultrathin, nearly monodisperse TiO2 (anatase) wires with tunable diameters of 5 nm to approximately 4 Å, reaching the atomic length scale. The high‐quality anatase titania atomically thin wires can be doped and stabilized with nitrogen species by introducing suitable nitrogen‐containing molecules. The ultrathin wires, particularly the atomically thin wires, as well as the precursor, have been thoroughly characterized by an extensive series of structural, spectroscopic, and other techniques. Possible formation mechanisms for the rods and the wires are proposed on the basis of experimental results obtained under varying reaction conditions. Also demonstrated are the pronounced effects of size and N‐doping on the electronic, optical, and phononic properties of the anatase titania wires in the smallest size regime.
Copper‐Containing SiCN Precursor Ceramics (Cu@SiCN) as Selective Hydrocarbon Oxidation Catalysts Using Air as an Oxidant
Authors: Glatz Germund , Schmalz Thomas , Kraus Tobias , Haarmann Frank , Motz Günter , Kempe Rhett 
Published: March 2010

AbstractA molecular approach to metal‐containing ceramics and their application as selective heterogeneous oxidation catalysts is presented. The aminopyridinato copper complex [Cu2(ApTMS)2] (ApTMSH=(4‐methylpyridin‐2‐yl)trimethylsilanylamine) reacts with poly(organosilazanes) via aminopyridine elimination, as shown for the commercially available ceramic precursor HTT 1800. The reaction was studied by 1H and 13C NMR spectroscopy. The liberation of the free, protonated ligand ApTMSH is indicative of the copper polycarbosilazane binding. Crosslinking of the copper‐modified poly(organosilazane) and subsequent pyrolysis lead to the copper‐containing ceramics. The copper is reduced to copper metal during the pyrolysis step up to 1000 °C, as observed by solid‐state 65Cu NMR spectroscopy, SEM images, and energy‐dispersive spectroscopy (EDS). Powder diffraction experiments verified the presence of crystalline copper. All Cu@SiCN ceramics show catalytic activity towards the oxidation of cycloalkanes using air as oxidant. The selectivity of the reaction increases with increasing copper content. The catalysts are recyclable. This study proves the feasibility of this molecular approach to metal‐containing SiCN precursor ceramics by using silylaminopyridinato complexes. Furthermore, the catalytic results confirm the applicability of this new class of metal‐containing ceramics as catalysts.
Construction of SnIV Porphyrin/Trinuclear Ruthenium Cluster Dyads Linked by Pyridine Carboxylates: Photoinduced Electron Transfer in the Marcus Inverted Region
Authors: Kojima Takahiko , Hanabusa Kakeru , Ohkubo Kei , Shiro Motoo , Fukuzumi Shunichi 
Published: March 2010

AbstractNovel conglomerates consisting of saddle‐distorted SnIV(DPP) (H2DPP=dodecaphenylporphyrin) complexes and μ3‐O‐centered and carboxylato‐bridged trinuclear RuIII clusters linked by pyridine carboxylates were synthesized and characterized. SnIV–DPP complexes with Cl−, OH−, and 3‐ and 4‐pyridine carboxylates ligands were characterized by spectroscopic methods and X‐ray crystallography. Reactions of [Sn(DPP)(pyridinecarboxylato)2] with trinuclear RuIII clusters gave novel conglomerates in moderate yields. The conglomerates are stable in solution as demonstrated by 1H NMR and electrospray ionization mass spectrometry (ESI‐MS) measurements, which show consistent spectra with those expected from their structures, and also by electrochemical measurements, which exhibit reversible multistep redox processes. This stability stems from the saddle distortion of the DPP2− ligand to enhance the Lewis acidity of the SnIV center that strengthens the axial coordination of the linker. The fast intramolecular photoinduced electron transfer from the SnIV(DPP) unit to trinuclear RuIII clusters, affording the electron‐transfer (ET) state {Sn(DPP.+)–RuIIRuIII2}, was observed by femtosecond laser flash photolysis. The lifetimes of ET states of the conglomerates were determined to be in the range 98–446 ps, depending on the clusters and energies of the ET states. The reorganization energy of the electron transfer was determined to be 0.58±0.08 eV in light of the Marcus theory of electron transfer. The rate constants of both the photoinduced electron transfer and the back electron transfer in the conglomerates fall in the Marcus inverted region due to the small reorganization energy of electron transfer.
Stabilization of High‐Valent FeIVS6‐Cores by Dithiocarbamate(1−) and 1,2‐Dithiolate(2−) Ligands in Octahedral [FeIV(Et2dtc)3−n(mnt)n](n−1)− Complexes (n=0, 1, 2, 3): A Spectroscopic and Density Functional Theory Computational Study
Authors: Milsmann Carsten , Sproules Stephen , Bill Eckhard , Weyhermüller Thomas , George Serena DeBeer , Wieghardt Karl 
Published: March 2010

AbstractA detailed spectroscopic and quantum chemical analysis is presented to elucidate the electronic structures of the octahedral complexes [Fe(Et2dtc)3−n(mnt)n]n− (1–4, n=3, 2, 1, 0) and their one‐electron oxidized analogues [Fe(Et2dtc)3−n(mnt)n](n−1)− (1ox–4ox); (mnt)2− represents maleonitriledithiolate(2−) and (Et2dtc)1− is the diethyldithiocarbamato(1−) ligand. By using X‐ray crystallography, Mössbauer spectroscopy, and Fe and S K‐edge X‐ray absorption spectroscopy (XAS) it is convincingly shown that, in contrast to our previous studies on [Fe(cyclam)(mnt)]1+ (cyclam=1,4,8,11‐tetraazacyclotetradecane), the oxidation of 1–4 is metal‐centered yielding the genuine FeIV complexes 1ox–4ox. For the latter complexes, a spin ground state of S=1 has been established by magnetic susceptibility measurements, which indicates a low‐spin d4 configuration. DFT calculations at the B3LYP level support this electronic structure and exclude the presence of a ligand π radical coordinated to an intermediate‐spin ferric ion. Mössbauer parameters and XAS spectra have been calculated to calibrate our computational results against the experiment. Finally, a simple ligand‐field approach is presented to correlate the structural features obtained from X‐ray crystallography (100 K) with the spectroscopic data.
ChemInform Abstract: Synthesis, Crystal Structure and Luminescent Properties of Titanium(IV)‐Doped Calcium Borostannates, CaSn1‐xTix(BO3)2.
Authors: Kawano Tetsuya , Yamane Hisanori 
Published: March 2010

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Structural and Magnetic Properties of DyCo5‐xGax Compounds.
Authors: Li J. Q. , Ao W. Q. , Liu F. S. , Zhang W. H. , Yan J. L. 
Published: March 2010

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.