bluuebunny/crossref_metadata_2025_split huggingface dataset:
C‐Halophosphaalkenes: Probing the range of stability and reactivity towards bromine
Authors: Goede S.J. , Dam M.A. , Bickelhaupt F. 
Published: September 2010

AbstractThe importance of steric protection for the stability of phosphaalkenes RP=CI2 (6) was investigated by varying the size of group R. The phosphaalkene IsP=CI2 (6b) (Is = 2,4,6‐triisopropylphenyl) could be prepared in 15% isolated yield by reaction of IsPCl2 and HCI3 with two equivalents of lithium diisopropylamide, in analogy to the synthesis of the stable, sterically more protected, Mes*P = CI2 (6a) (Mes* = 2,4,6‐tri‐tert‐butylphenyl). If the steric protection on the phosphorus was decreased further (R = Es = 2,4,6‐triethylphenyl, R = Mes = 2,4,6‐trimethylphenyl), the substitution products RP(Cl)N(Pri)2 (R = Es (9c) or Mes (9d)) were formed as main products, in addition to thermally unstable phosphaalkenes EsP=CI2 (6c) and MesP=CI2 (6d). The structures of 9c‐d were corroborated by independent synthesis from RPCl2 and two equivalents of diisopropylamine.The reaction of 6awith bromine gave an E/Z mixture of the C‐bromo‐C‐iodophosphaalkene (EZ)‐Mes* P = CBrI (E/Z‐10). Further reaction with bromine proceeded via Mes*P=CBr2 (5a) and finally led to Mes* P(Br)(CHBr2) (12).
Synthesis of and vesicle formation from phosphorylcholine amphiphiles with one symmetrically branched alkyl chain
Authors: Overmars Franc J. J. , Engberts Jan B. F. N. , Weringa Wilke D. 
Published: September 2010

AbstractThree phosphorylcholines with symmetrically branched alkyl chains [(CnH2n + 1)2 CHOPO3−(CH2)2N(CH3)3+] (1a‐c) have been synthesized. The synthesis involves three steps: (1) reaction of the alcohol (CnH2n + 1)2CHOH, (n = 6, 8, 10) with 2‐chloro‐1,3,2‐dioxaphospholane in the presence of triethylamine; (2) oxidation of the resulting trialkyl phosphite with nitrogen dioxide and (3) ring opening of the cyclic phosphate triester by trimethylamine in acetonitrile. When suspended in water, these amphiphiles all form bilayer vesicles as revealed by electron microscopy and NMR spectroscopy. The vesicles have diameters of 300‐1000 Å and are stable for more than a week.
Enzymatic synthesis of specifically 2H‐labelled L‐glutamic acids and 2H‐, 15N‐, 13C‐labelled L‐glutamines on a preparative scale
Authors: Ogrel A. , Vasilenko I. A. , Lugtenburg J. , Raap J. 
Published: September 2010

AbstractIn this paper we report the preparation of specifically 2H‐labelled L‐glutamic acids and 2H‐, 15N‐, 13C‐labelled L‐glutamines on the gram scale. The products obtained have high isotope enrichment (>98%) and high optical purity. The synthetic schemes allow the specific isotope enrichment of every H, C, and N position or any combination of positions. (2‐2H)‐L‐Glutamic acid was synthesized by enantioselective enzymatic conversion of 2‐oxoglutaric acid using glutamate dehydrogenase (GDH, E.C. 1.4.1.3.), alcohol dehydrogenase (ADH, E.C. 1.1.1.1.) and (2H6)ethanol. (3,3‐2H2)‐L‐Glutamic acid was prepared by enzymatic conversion of 2‐oxo‐3,3‐di‐deuteroglutaric acid which was easily obtained from 2‐oxoglutaric acid by an isotope exchange reaction in 2H2O at pH 13.0. (4,4‐2H2)‐L‐Glutamic acid was obtained by chemical exchange in 20% 2HCl. Four different isotopomers of L‐glutamine [(2‐2H)‐, (3,3‐2H2)‐, (4,4‐2H2)‐, and (5‐13C)‐L‐Gln] were synthesized by the enantioselective conversion of isotopically labelled L‐glutamic acids using glutamine synthetase (GS, E.C. 6.3.1.2.). The amide group of glutamine was labelled with 15N using 15NH4Cl in the enzymatic reaction. The labelled L‐glutamic acids and L‐glutamines were characterized by 1H‐NMR, 13C‐NMR and mass spectrometry.
Dramatic acceleration of alkylation reactions with organolithium compounds by potassium tert‐butoxide
Authors: Brandsma L. , Mal'kina A.G. , Lochmann L. , Schleyer P. Von R. 
Published: September 2010

AbstractReactions of organolithium compounds with alkyl halides and with epoxides are considerably accelerated by addition of equivalent amounts of potassium tert‐butoxide.
Synthesis and characterization of all‐E (12,12′‐13C2)‐, (13,13′‐13C2)‐, (14,14′‐13C2)‐, (15,15′‐13C2)‐ and (20,20′‐13C2)astaxanthin
Authors: Jansen F.J.H.M. , Kwestro M. , Schmitt D. , Lugtenburg J. 
Published: September 2010

AbstractThe all‐E isomers of (12,12′‐13C2)‐, (13,13′‐13C2)‐, (14,14′‐13C2)‐, (15,15′‐13C2)‐ and (20,20′‐13C2)astaxanthin were prepared by total synthesis starting from commercially available 99% 13C‐enriched acetonitrile, acetic acid and methyl iodide. The astaxanthins were obtained in high purity and with high isotope incorporation (> 99% for every position). For this synthesis, the C15 + C10 + C15 strategy was used. The central C10‐synthon, 2,7‐dimethylocta‐2,4,6‐triene‐1,8‐dial, was symmetrically dilabelled at any position using two new synthetic schemes. The 13C2‐enriched C10‐dialdehydes were then converted in one step to the 13C2‐enriched astaxanthins.
A novel approach towards the synthesis of pyrophosphate analogues of farnesyl pyrophosphate
Authors: Valentijn A.R.P.M. , van den Berg O. , van der Marel G.A. , van Boom J.H. , Cohen L.H. 
Published: September 2010

AbstractThe synthesis of two new analogues (i.e. 3 and 4) of farnesyl pyrophosphate (FPP) containing a phosphonophosphate and a phosphonophosphonate moiety was accomplished via the phosphonomorpholidate. The latter was easily obtained by treatment of a phosphonic chloride with morpholine.
Synthesis of chiral sulfines by oxidation of dithio esters
Authors: van der Linden Johannes B. , Timmermans Johan L. , Zwanenburg Binne 
Published: September 2010

AbstractThe synthesis of sulfines (thione oxides) (2, 10 and 17) derived from three chiral dithio esters (1, 8 and 16) bearing a hydrogen at the α‐carbon atom is described. The sulfine bearing an amido group at C‐α (2), does not racemize and proved to be stable over a long period. When C‐α in the sulfine (10) bears an acetoxy group the optical activity remained unchanged for a period of two months; after longer storage a rearrangement to a mixture of dithioperoxy ester 12 and S‐methyl ester 11 took place. With an alkyl group at C‐α, the sulfine 17 undergoes a fast racemization and rearranges slowly to a mixture of S‐ethyl ester 14, dithioperoxy ester 18 and S‐vinyl thiosulfinate 19.
Synthesis of potential receptor molecules by combination of upper‐rim‐functionalized calix[4]arenes and partly bridged resorcinarenes
Authors: Timmerman Peter , Boerrigter Harold , Verboom Willem , Reinhoudt David N. 
Published: September 2010

AbstractCombination of upper‐rim‐1,3‐difunctionalized calix[4]arenes 14, 16, and 18 with tribridged resorcinarenes 4 and 6 and A,C‐di‐bridged resorcinarenes 10 and 13 yields both 1/1 calix‐resorcinarenes (22–24) and 2/1 calix‐resorcinarenes (25, 26). 1/1 Calix‐resorcinarene 22 mainly exists as one conformer (a), but at low temperatures (−60°C) very small amounts ( < 5%) of a second conformer (b) can be observed. Both conformers equilibrate via rotation about one of the C(arene)‐N bonds, with an activation free energy (Δ G≠) of 13 kcal/mol. 2/1 Calix‐resorcinarenes 25 and 26 are more flexible and exist as a mixture of conformers. In order to be able to rigidify the structure of 2/1 calix‐resorcinarenes via rigid spacers between the calix[4]arene fragments, 1,3‐diaminocalix[4]arene derivatives 31, 32, and 34 were synthesized carrying nitro, carboxylic ester, and cyano groups at the unsubstituted aromatic rings. With these calix[4]arene derivatives, three new, functionalized 2/1 calix‐resorcinarenes 35–37 have been synthesized.
Syn‐Stereocontrolled dihydroxylation of Baylis‐Hillman adducts
Authors: Markó István E. , Giles Paul R. , Janousek Zdenek , Hindley Nigel J. , Declercq Jean‐Paul , Tinant Bernard , Feneau‐Dupont Janine , Svendsen John S. 
Published: September 2010

AbstractThe hydroxylation of Baylis‐Hillman adducts 1 is shown to proceed with high levels of diastereocontrol. A mechanistic rationale to explain this selectivity is discussed.
Ruthenium diphosphine complexes for catalysis; a general synthesis and direct comparisons with rhodium complexes
Authors: Brown John M. , Rose Michael , Knight Frances I. , Wienand Anette 
Published: September 2010

AbstractA method for the preparation of diphosphineruthenium complexes from a range of diphosphine precursors is described. The stable products, of general formula P2Ru(allyl)acac (P = phosphine ligand), do not catalyse the hydrogenation of alkenes but can easily be converted into catalytically active species by reaction with trimethylsilyl trifluoromethanesulfonate. The chemistry involved in this transformation is discussed. Catalysis of the hydrogenation of a range of alkenes, and direct comparison with related rhodium reductions, is described. Some mechanistic insights are gained through additions of D2 to alkenes and parallel hydrogenations on deuterated solvent, supporting the intervention of conventional dihydride and alkyl hydride intermediates which undergo exchange with solvent at both stages.
Inversion of enantioselectivity of serine proteases
Authors: Broos Jaap , Engbersen Johan F. J. , Verboom Willem , Reinhoudt David N. 
Published: September 2010

AbstractThe enantioselectivity of serine proteases in the transesterification of N‐acetyl‐(D,L)‐ phenylalanine esters with propan‐1‐ol in cyclohexane is strongly influenced by the leaving ability of the alcoholate group. Moreover the enantioselectivity is greatly influenced by the addition of small amounts (0.33 M) of organic additives. Addenda with a small molecular volume like e.g. ethanol and acetonitrile increase the rate for the L‐enantiomer whereas alcohols with bulky alkyl groups like e.g. tert‐butanol and 2‐methylbutan‐2‐ol enhance the activity of the enzyme towards the D‐enantiomer. This enables a rational tuning of the enantioselectivity as was demonstrated for four different proteases (α‐chymotrypsin, subtilisin Carlsberg, Aspergillus oryzae protease, and elastase).
Synthesis of new macrocyclic ligands for hetero‐multinuclear transition‐metal complexes
Authors: Huck Wilhelm T. S. , van Veggel Frank C. J. M. , Reinhoudt David N. 
Published: September 2010

AbstractThe [3 + 3] macrocyclic compounds 2a–2c were easily prepared by cyclization of the dialdehyde 8 with the appropiate diamines in refluxing CH3CN/MeOH (1/1), in the presence of Ba2+ as a template ion. These macrocycles contain three salen units and are therefore, in combination with the crown ether interior, potentially tetranucleating. The length of the diamine bridge and the temperature at which the reaction is carried out, appear to influence the size of the macrocycle formed. In this way, the [4 + 4] macrocycle 2d could be formed selectively over the [3 + 3] macrocycles by carrying out the reaction at room temperature.
Metal ion induced disintegration of a pyrazole‐containing ligand and formation of an unprecedented pyrazolato‐bridged di‐zinc anion. The X‐ray structure of the mixed ligand compound bis [(1,6‐bis(3,5‐dimethylpyrazol‐1‐yl)‐2,5‐dimethyl‐2,5‐diazahexane)‐(chloro)zinc(chloro) zinc(II)] [bis(μ‐3,5‐dimethylpyrazolato) tetrachlorodizincaat(II)], [Zn(C16H28N6)Cl]2[Zn2(C5H7N2)2Cl4]
Authors: Driessen W. L. , Paap F. , Reedijk J. 
Published: September 2010

AbstractThe ligand 1,6‐bis(3,5‐dimethylpyrazol‐1‐yl)‐2,5‐dimethyl‐2,5‐diazahexane (debd), which has been synthesized from 3,5‐dimethylpyrazole, N,N′‐dimethylethanediamine and formaldehyde, partially disintegrates when reacted with zinc dichloride or with zinc dibromide in methanol. The resulting compounds contain the unique bis(pyrazolato)‐bridged tetrahalogenido dizinc(II) anion. The compound [Zn(debd)Cl]2[Zn2(dmpz)2Cl4], with formula C42H70Cl6N16Zn4 and Mr = 1273.36, is obtained from methanol as monoclinic crystals, spacegroup P 21/c with a = 15.990(2) Å, b = 16.394(2) Å, c = 12.006(1) Å, β = 100.61(1)°, V = 3093.4(5) Å3, Zm = 2, Dx = 1.37 g.cm−3, as measured at room temperature with Mo(Kα) radiation to a final R value of 0.062 (wR = 0.065) for 2465 significant [I > 2σ‐(I)] reflections.The asymmetric unit comprises half the formula unit. The cation consists of a Zn2+ ion in a distorted trigonal bipyramidal environment of a chloride ion at 2.221(3) Å, an amine nitrogen at 2.17(1) Å and a pyrazole nitrogen at 2.05(1) Å in the equatorial plane, with an amine nitrogen at 2.27(1) and a pyrazole nitrogen at 2.14(1) Å in the axial positions. The largest distortion is in the axis of the trigonal bipyramide with an N‐Zn‐N angle of 150.2(5)°.The anion consists of two Zn2+ ions, which are bridged by two deprotonatedThe authors realise that the recommended IUPAC term is (de)hydronated instead of (de)protonated to indicate loss/addition of H+.
dimethylpyrazole ligands with N‐Zn distances of 1.97(1) and 1.98(1) Å, while each Zn2+ ion is further bound to two chloride ions at 2.276(4) and 2.261(4) Å. The Zn2+ ions are in an almost regular N2Cl2 tetrahedron.
Reactions of cyclic nitrones with (E)‐γ‐hydroxy‐ and (E)‐γ‐alkoxy‐α,β‐unsaturated esters
Authors: de March P. , Figueredo M. , Font J. , Monsalvatje M. 
Published: September 2010

AbstractThe 1,3‐dipolar cycloadditions of 2,3,4,5‐tetrahydropyridine 1‐oxide (1) and 3,4‐dihydro‐2H‐pyrrole 1‐oxide (2) to methyl (E)‐6‐(benzyloxy)‐4‐hydroxy‐2‐hexenoate (3) and methyl (S)‐(E)‐3‐(2,2‐dimethyl‐1,3‐dioxolan‐4‐yl)propenoate (4) yield predominantly the adducts derived from endo transition states with antifacial approaches.
Intellectual property protection and the formation of entrepreneurial growth aspirations
Authors: Autio Erkko , Acs Zoltan 
Published: September 2010

AbstractApplying real options logic, we build and test a multilevel model that explicates the influence of a country's intellectual property protection regime on the effect of an individual's human and financial capital on entrepreneurial growth aspirations. The results suggest that the strength of the intellectual property regime moderates negatively the relationship between an individual's education and entrepreneurial growth aspirations; and it moderates positively the relationship between an individual's household income and growth aspirations. Intellectual property protection, thereby, encourages specialization amongst differently qualified entrepreneurs. Our findings support claims that strategic entrepreneurial behaviors cannot be fully understood without giving attention to the context in which those behaviors are observed. Copyright © 2010 Strategic Management Society.
Parent firm effects on founder turnover: parent success, founder legitimacy, and founder tenure
Authors: Boeker Warren , Fleming Brandon 
Published: September 2010

AbstractEmpirical studies examining new ventures have demonstrated a significant degree of founder turnover after start‐up as founders are replaced by ‘professional’ managers. We examine how founders' past experience in their prior employer (their parent firm) affects their tenure in the new venture. Founders coming from more successful parent firms, with more prior affiliations among the venture's cofounders and with prior start‐up experience are more likely to remain with the new venture after founding. These effects are more pronounced in cases where the technologies employed by the start‐up are more uncertain. Copyright © 2010 Strategic Management Society.
Study on the biological effect of Tourmaline on the cell membrane of E. coli
Authors: Qiu Shan , Ma Fang , Wo Yuan , Xu Shanwen 
Published: September 2010

AbstractThe biological effect of tourmaline on the cell membrane of E. coli by microcalorimetry, fluorescence polarization, ion analysis and fourier transform infrared was studied. It was observed that tourmaline of low concentration can promote growth of the bacteria, while tourmaline of high concentration has inhibitory effects on E. coli. Fluorescence polarization has shown a significant decrease in membrane fluidity and the increase of permeability of cell membrane. The ion analysis result suggested that the absorbability of nutrition from the medium becomes easier. Thus, E. coli grew faster in the presence of tourmaline than the native. With high concentration of tourmaline, however, the growth of E. coli was inhibited because the selective barrier of cell membrane for the bacteria was seriously damaged. Besides, changes of the spectral profile of E. coli were observed, which has shown the damages of surface groups on the cell membrane, which is the molecular basis for the biological effect of tourmaline. Copyright © 2010 John Wiley & Sons, Ltd.
Form und Tragverhalten hyperbolischer Gittertürme
Authors: Beckh Matthias , Hoheisel Meike 
Published: September 2010

AbstractMit dem im Jahr 1989 von Rainer Graefe, Murat Gappoev und Ottmar Pertschi herausgegebenen Buch “Die Kunst der sparsamen Konstruktion” ist das Werk des russischen Leichtbaupioniers Vladimir G. Šuchov in das Bewusstsein des deutschsprachigen Fachpublikums getreten. Seit 2007 werden am Lehrstuhl für Tragwerksplanung der Technischen Universität München (Prof. Dr.‐Ing. Rainer Barthel) die hyperbolischen Turmstrukturen von Vladimir G. Šuchov untersucht. Neben der Dokumentation der bestehenden Türme und der Analyse der originalen Planunterlagen und Berechnungen bilden die Untersuchungen zum Tragverhalten der Türme einen wichtigen Bestandteil der Arbeit. Im folgenden Beitrag soll die Tragwirkung von einstöckigen hyperbolischen Gittertürmen sowie die Wechselwirkungen zwischen Form und Tragverhalten aufgezeigt werden.Interaction of form and structural behaviour of hyperboloid lattice towers. The renown Russian engineer Vladimir Shukhov invented and patented in 1896 the hyperboloid lattice tower. In the following four decades he built about 200 towers with his new system. Most of them served as water towers, others were built as lighthouses or radio stations. Form and structure of these towers varies depending on their location and purpose. The geometry of hyperboloid lattice towers is based on five key parameters. The authors undertook an extensive parameter study to explore the interdependencies between the key parameters and their effect on the ultimate bearing load of the structure. Apart from the lattice configuration that was employed by Shukhov, two alternative options are discussed.
Friction connection in tubular towers for a wind turbine
Authors: Veljkovic Milan , Feldmann Markus , Naumes Johannes , Pak Daniel , Rebelo Carlos , Simões da Silva Luís 
Published: September 2010

AbstractInnovative solution for assembling joints of a tubular tower for wind turbines has been studied by a European consortium since 2005 and the HISTWIN (High‐Strength Steel Tower for Wind Turbine) project provides background for design of the friction connection considered. This solution is simpler to produce and 80% less expensive than traditional flange connection. A feasibility study at the production plant indicates that the towers would be easy to assemble in‐situ. In addition to the direct costs savings due to technical simplicity of the solution, the higher fatigue endurance than the flange connection is experimentally established. The loss of pretension forces in the friction connection with long opened slotted holes is studied using segment shortterm and long‐term static tests, fatigue tests, down‐scaled bending tests and by a specimen used in a feasibility study. The total reduction of the costs for tower is estimated to about 10% to 15% compared to the traditional tower with the flange connection.Reibverbindung für Türme von Windenergieanlagen. Im Rahmen des europäischen RFCS (Research Fund for Coal and Steel) Projektes HISTWIN wird seit 2005 eine innovative Reibverbindung für Verbindungsstöße von Windenergieanlagen entwickelt und untersucht. Im Vergleich zur konventionellen Flanschverbindung ist die untersuchte Lösung sowohl einfacher als auch kostengünstiger herzustellen, wobei mit Einsparungen von bis zu 80% für die Verbindung gerechnet wird. Der problemlose Zusammenbau vor Ort wurde durch eine im Werk durchgeführte Machbarkeitsstudie überprüft. Weiterhin wurden experimentelle Untersuchungen zur im Vergleich zu konventionellen Flanschverbindungen höheren Ermüdungsbeanspruchbarkeit der Verbindungsmittel durchgeführt. Der Vorspannkraftverlust in der Langlochverbindung wurde auf Basis von statischen Kurzzeit‐ und Langzeitversuchen, Ermüdungsversuchen sowie skalierten 4‐Punkt Biegeversuchen untersucht. Die sich aus der neuen Verbindung ergebenden Kosteneinsparungen belaufen sich auf ca. 10 bis 15%.
Three Novel 1‐H‐Benzimidazole‐5‐Carboxylate‐Based Nickel(II)/Cobalt(II) Coordination Polymers: Synthesis, Crystal Structures, Luminescent, and Magnetic Properties
Authors: Zhao Li‐Na , Liu Tian‐Yu , Liu Zhong‐Yi , Yang En‐Cui , Zhao Xiao‐Jun 
Published: September 2010

AbstractThree 1H‐benzimidazole‐5‐carboxylate (Hbic–)‐based coordination polymers, {[Ni(H2O)(Hbic)2]·2H2O}n (1), {[Ni(H2O)2(Hbic)2]·3H2O}n (2), and {[Co2(H2O)4(Hbic)4]·4DMF·3H2O}n (3) were obtained by reactions of the ligand H2bic and NiII or CoII salts in the presence of different structure directing molecules. They were structurally characterized by single‐crystal X‐ray diffraction, IR spectra, elemental analysis, thermal stability, luminescent, and magnetic measurements. Structural analysis suggests that the three polymers exhibit a 2D (4, 4) layer for 1 and 1D linear double chains for both 2 and 3 due to the variable binding modes and the specific spatial orientation of the Hbic– ligand towards the different paramagnetic metal ions, which were further aggregated into different 3D supramolecular architectures by popular hydrogen‐bonding interactions. Weak and comparable antiferromagnetic couplings mediating by Hbic– bridge are observed between the neighboring spin carriers for 2 and 3, respectively. Additionally, complexes 1–3 also display different luminescence emissions at room temperature due to the ligand‐to‐metal charge transfer.
Presence and Persistence of Nutrition‐Related Symptoms During the First Year Following Esophagectomy with Gastric Tube Reconstruction in Clinically Disease‐Free Patients
Authors: Haverkort E. B. , Binnekade J. M. , Busch O. R. C. , van Berge Henegouwen M. I. , de Haan R. J. , Gouma D. J. 
Published: September 2010

AbstractBackgroundEsophagectomy with gastric tube reconstruction results in a variety of postoperative nutrition‐related symptoms that may influence the patient’s nutritional status.MethodsWe developed a 15‐item questionnaire, focusing on the nutrition‐related complaints the first year after an esophagectomy. The questionnaire was filled out the first week after discharge and 3, 6, and 12 months after surgery. The use of enteral nutrition, meal size and frequency, social aspects related to eating, defecation pattern, and body weight were recorded at the same time points. We analyzed the relationship between the baseline characteristics and the number of nutrition‐related symptoms, as well as the relationship between those symptoms and body weight with linear mixed models.ResultsWe found no significant within‐patient change for the total number of nutrition‐related symptoms (P = 0.67). None of the baseline factors were identified as predictors of the complaint scores. The most frequently experienced complaints were early satiety, postprandial dumping syndrome, inhibited passage due to high viscosity, reflux, and absence of hunger. One year after surgery, meal sizes were still smaller, the social aspects of eating were influenced negatively, and patients experienced an altered stool frequency. Directly after the surgical procedure 78% of the patients lost weight, and the entire postoperative year the mean body weight remained lower (P = 0.47). We observed no association between the complaint scores and body weight (P = 0.15).ConclusionsAfter an esophagectomy, most patients struggle with nutrition‐related symptoms, are confronted with nutrition‐related adjustments and a reduced body weight.