bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potential Analysis of Smart Flow Processing and Micro Process Technology for Fastening Process Development: Use of Chemistry and Process Design as Intensification Fields
Authors: Hessel V. , Vural Gürsel I. , Wang Q. , Noël T. , Lang J. 
Published: June 2012

AbstractFlow processes with microstructured reactors allow paradigm changes in process development and thus can enable a faster development time to the final production plant. They do this by exploiting similarity effects along the development chain (modularity) and intensification. The final result can be a (significantly) reduced number of apparatus in the plant, a (significantly) reduced apparatus size, and a higher predictability in the scale‐out of the apparatus. So far, this was mainly achieved via transport intensification given in microstructured reactors – improved mixing and heat transfer which increase productivity and possibly improve selectivity. A more new idea is chemical intensification through deliberate use of harsh chemistries at unusual (high) pressure, temperature, concentration, and reaction environment which again increases productivity. A very new idea is the process design intensification – the reaction‐maximized flow processes need less separation expenditure and the small unit size together with the high degree in functionality gives large potential for system integration. Both means change and simplify the process scheme totally which can lead to a reduced number of apparatus and has impact on predictability. The modular nature of the small flow units allow an easy implementation to modern modular plant environments (Future Factories) which enables to perform all the testing cycles (lab, pilot, production) in one plant environment; an example are here container plants. All these measures have large potential for (much) decreased overall development time.
Semicontinuous Thermal Separation Systems
Authors: Adams T. A. , Pascall A. 
Published: June 2012

AbstractSince the year 2000, semicontinuous separation processes have been studied as a unique process intensification technique for the thermal separation of chemical mixtures. Typically, a single separation unit is used for multiple purposes with the aid of an auxiliary storage tank called a middle vessel. The system is operated cyclically but without startup or shutdown phases. As a result, multiple separation steps can be carried out with fewer capital expenses. In several cases, a significant profitability advantage over continuous or batch process alternatives has been shown, particularly for intermediate production capacities. The progress in semicontinuous systems is reviewed, including the development of semicontinuous ternary distillation, liquid‐liquid extraction, azeotrope distillation, reactive distillation, and semicontinuous systems with integrated reaction and distillation or extraction. Control and operational strategies for semicontinuous systems are reviewed, as well as heuristics for modeling and simulation.
Scalable Syntheses of Both Enantiomers of DNJNAc and DGJNAc from Glucuronolactone: The Effect of N‐Alkylation on Hexosaminidase Inhibition
Authors: Glawar Andreas F. G. , Best Daniel , Ayers Benjamin J. , Miyauchi Saori , Nakagawa Shinpei , Aguilar‐Moncayo Matilde , García Fernández José M. , Ortiz Mellet Carmen , Crabtree Elizabeth V. , Butters Terry D. , Wilson Francis X. , Kato Atsushi , Fleet George W. J. 
Published: June 2012

AbstractThe efficient scalable syntheses of 2‐acetamido‐1,2‐dideoxy‐D‐galacto‐nojirimycin (DGJNAc) and 2‐acetamido‐1,2‐dideoxy‐D‐gluco‐nojirimycin (DNJNAc) from D‐glucuronolactone, as well as of their enantiomers from L‐glucuronolactone, are reported. The evaluation of both enantiomers of DNJNAc and DGJNAc, along with their N‐alkyl derivatives, as glycosidase inhibitors showed that DGJNAc and its N‐alkyl derivatives were all inhibitors of α‐GalNAcase but that none of the epimeric DNJNAc derivatives inhibited this enzyme. In contrast, both DGJNAc and DNJNAc, as well as their alkyl derivatives, were potent inhibitors of β‐GlcNAcases and β‐GalNAcases. Neither of the L‐enantiomers showed any significant inhibition of any of the enzymes tested. Correlation of the in vitro inhibition with the cellular data, by using a free oligosaccharide analysis of the lysosomal enzyme inhibition, revealed the following structure–property relationship: hydrophobic side‐chains preferentially promoted the intracellular access of iminosugars to those inhibitors with more‐hydrophilic side‐chain characteristics.
Discrete Cationic Zinc and Magnesium Complexes for Dual Organic/Organometallic‐Catalyzed Ring‐Opening Polymerization of Trimethylene Carbonate
Authors: Brignou Pierre , Guillaume Sophie M. , Roisnel Thierry , Bourissou Didier , Carpentier Jean‐François 
Published: June 2012

AbstractWe describe herein an original approach for the efficient immortal ring‐opening polymerization (iROP) of trimethylene carbonate (TMC) under mild conditions using dual‐catalyst systems combining a discrete cationic metal complex with a tertiary amine. A series of new zinc and magnesium cationic complexes of the type [{NNO}M]+[anion]− ({NNO}−=2,4‐di‐tert‐butyl‐6‐{[(2′‐dimethylaminoethyl)methylamino]methyl}phenolate; M=Zn, [anion]−=[B(C6F5)4]− (2), [H2N‐ {B(C6F5)3}2]− (3), and [EtB(C6F5)3]− (4); M=Mg, [anion]−=[H2N{B(C6F5)3}2]− (7)) have been prepared from the corresponding neutral compounds [{NNO}ZnEt] (1) and [{NNO}‐ Mg(nBu)] (6). Compounds 2–4 and 7 exist as free ion pairs, as revealed by 1H, 13C, 19F, and 11B NMR spectroscopy in THF solution, and an X‐ray crystallographic analysis of the bis(THF) adduct of compound 7, 7⋅(THF)2. The neutral complexes 1 and 6, in combination with one equivalent or an excess of benzyl alcohol (BnOH), initiate the rapid iROP of TMC, in bulk or in toluene solution, at 45–60 °C (turnover frequency, TOF, up to 25–30 000 mol(TMC)⋅mol(Zn)⋅h−1 for 1 and 220–240 000 mol(TMC)⋅mol(Mg)⋅h−1 for 6), to afford H‐PTMC‐OBn with controlled macromolecular features. ROP reactions mediated by the cationic systems 2/BnOH and 7/BnOH proceeded much more slowly (TOF up to 500 and 3 000 mol(TMC)⋅mol(Zn or Mg)⋅h−1 at 110 °C) than those based on the parent neutral compounds 1/BnOH and 6/BnOH, respectively. Use of original dual organic/organometallic catalyst systems, obtained by adding 0.2–5 equiv of a tertiary amine such as NEt3 to zinc cationic complexes [{NNO}Zn]+[anion]− (2–4), promoted high activities (TOF up to 18 300 mol(TMC)⋅mol(Zn)⋅h−1 at 45 °C) giving H‐PTMC‐OBn with good control over the Mn and Mw/Mn values. Variation of the nature of the anion in 2–4 did not significantly affect the performance of these catalyst systems. On the other hand, the dual magnesium‐based catalyst system 7/NEt3 proved to be poorly effective.
Enantioselective Synthesis of AG‐041R by using N‐Heteroarenesulfonyl Cinchona Alkaloid Amides as Organocatalysts
Authors: Hara Noriyuki , Nakamura Shuichi , Sano Masahide , Tamura Ryota , Funahashi Yasuhiro , Shibata Norio 
Published: June 2012

AbstractThe organocatalytic enantioselective decarboxylative addition of malonic acid half thioesters to ketimines derived from isatins by using N‐heteroarenesulfonyl cinchona alkaloid amides afforded products with high enantioselectivity. The products could be converted into optically active AG‐041R. X‐ray crystallographic analysis revealed that the hydrogen bonding between the sulfonimide proton and the 8‐quinolyl nitrogen atom plays an important role in exerting the enantioselectivity of the reaction.
Ensemble‐Averaged QM/MM Kinetic Isotope Effects for the SN2 Reaction of Cyanide Anions with Chloroethane in DMSO Solution
Authors: Ruiz Pernía J. Javier , Williams Ian H. 
Published: June 2012

AbstractThe existence of solvent fluctuations leads to populations of reactant‐state (RS) and transition‐state (TS) configurations and implies that property calculations must include appropriate averaging over distributions of values for individual configurations. Average kinetic isotope effects 〈KIE〉 for NC−+EtCl→NCEt+Cl− in DMSO solution at 30 °C are best obtained as the ratio 〈fRS〉/〈fTS〉 of isotopic partition function ratios separately averaged over all RS and TS configurations. In this way the hybrid AM1/OPLS‐AA potential yields 〈KIE〉 values for all six isotopic substitutions (2° α‐2H2, 2° β‐2H3, α‐11C/14C, leaving group 37Cl, and nucleophile 13C and 15N) for this reaction in the correct direction as measured experimentally. These thermally‐averaged calculated KIEs may be compared meaningfully with experiment, and only one of them differs in magnitude from the experimental value by more than one standard deviation from the mean. This success contrasts with previous KIE calculations based upon traditional methods without averaging. The isotopic partition function ratios are best evaluated using all (internal) vibrational and (external) librational frequencies obtained from Hessians determined for subsets of atoms, relaxed to local minima or saddle points, within frozen solvent environments of structures sampled along molecular dynamics trajectories for RS and TS. The current method may perfectly well be implemented with other QM or QM/MM methods, and thus provides a useful tool for investigating KIEs in relation to studies of chemical reaction mechanisms in solution or catalyzed by enzymes.
Synthesis, Characterization, and Application of Two Al(ORF)3 Lewis Superacids
Authors: Kraft Anne , Trapp Nils , Himmel Daniel , Böhrer Hannes , Schlüter Peter , Scherer Harald , Krossing Ingo 
Published: June 2012

AbstractWe report herein the synthesis and full characterization of the donor‐free Lewis superacids Al(ORF)3 with ORF=OC(CF3)3 (1) and OC(C5F10)C6F5 (2), the stabilization of 1 as adducts with the very weak Lewis bases PhF, 1,2‐F2C6H4, and SO2, as well as the internal CF activation pathway of 1 leading to Al2(F)(ORF)5 (4) and trimeric [FAl(ORF)2]3 (5, ORF=OC(CF3)3). Insights have been gained from NMR studies, single‐crystal structure determinations, and DFT calculations. The usefulness of these Lewis acids for halide abstractions has been demonstrated by reactions with trityl chloride (NMR; crystal structures). The trityl salts allow the introduction of new, heteroleptic weakly coordinating [Cl‐Al(ORF)3]− anions, for example, by hydride or alkyl abstraction reactions.
Fluorescent Microporous Organic Polymers: Potential Testbed for Optical Applications
Authors: Patra Abhijit , Scherf Ullrich 
Published: June 2012

AbstractFluorescent microporous organic polymers (MOPs) are an emerging class of porous organic materials with considerable technological relevance due to great promise in a range of applications, in addition to typical usage in gas storage and catalysis. In this respect, innovative optical materials have been developed based on MOPs. In this Concept article, a brief appraisal of the fabrication methodologies of fluorescent MOPs in the form of bulk solid as well as in nanoparticles, their optical attributes, and promising application potentials are presented.
From lin‐Benzoguanines to lin‐Benzohypoxanthines as Ligands for Zymomonas mobilis tRNA–Guanine Transglycosylase: Replacement of Protein–Ligand Hydrogen Bonding by Importing Water Clusters
Authors: Barandun Luzi Jakob , Immekus Florian , Kohler Philipp C. , Tonazzi Sandro , Wagner Björn , Wendelspiess Severin , Ritschel Tina , Heine Andreas , Kansy Manfred , Klebe Gerhard , Diederich François 
Published: June 2012

AbstractThe foodborne illness shigellosis is caused by Shigella bacteria that secrete the highly cytotoxic Shiga toxin, which is also formed by the closely related enterohemorrhagic Escherichia coli (EHEC). It has been shown that tRNA–guanine transglycosylase (TGT) is essential for the pathogenicity of Shigella flexneri. Herein, the molecular recognition properties of a guanine binding pocket in Zymomonas mobilis TGT are investigated with a series of lin‐benzohypoxanthine‐ and lin‐benzoguanine‐based inhibitors that bear substituents to occupy either the ribose‐33 or the ribose‐34 pocket. The three inhibitor scaffolds differ by the substituent at C(6) being H, NH2, or NHalkyl. These differences lead to major changes in the inhibition constants, pKa values, and binding modes. Compared to the lin‐benzoguanines, with an exocyclic NH2 at C(6), the lin‐benzohypoxanthines without an exocyclic NH2 group have a weaker affinity as several ionic protein–ligand hydrogen bonds are lost. X‐ray cocrystal structure analysis reveals that a new water cluster is imported into the space vacated by the lacking NH2 group and by a conformational shift of the side chain of catalytic Asp102. In the presence of an N‐alkyl group at C(6) in lin‐benzoguanine ligands, this water cluster is largely maintained but replacement of one of the water molecules in the cluster leads to a substantial loss in binding affinity. This study provides new insight into the role of water clusters at enzyme active sites and their challenging substitution by ligand parts, a topic of general interest in contemporary structure‐based drug design.
Capturing the Antiaromatic #6094C68 Carbon Cage in the Radio‐Frequency Furnace
Authors: Amsharov Konstantin Yu. , Ziegler Karolin , Mueller Andreas , Jansen Martin 
Published: June 2012

AbstractAlthough all fullerenes do not satisfy the classical aromaticity condition, as a result of their nonplanar nature, they experience effective stabilization due to extensive cyclic π‐electron delocalization and exhibit pronounced “spherical aromaticity”. This feature has raised the question of the opposite phenomenon, that is, the existence of antiaromatic carbon cages. Here the first experimental evidence of the existence of antiaromatic fullerenes is reported. The elusive #6094C68 was effectively captured as C68Cl8 by in situ chlorination in the gas phase during radio‐frequency synthesis. The chlorinated cage was separated by means of multistage HPLC, and its connectivity unambiguously determined by single‐crystal X‐ray analysis. Halogen‐stripped pristine #6094C68 was monitored by mass spectrometry of the chlorinated C68Cl8 cage. Quantum chemical calculations reveal the highly antiaromatic character of #6094C68, in accordance with all geometric, energetic, and magnetic criteria of aromaticity. Chlorine addition leads to substantial stabilization of the cage owing to aromatization in the resulting C68Cl8, which explains its high abundance in the primary fullerene soot. This work provides new insights into the process of fullerene formation and better understanding of aromaticity phenomena in general.
A Substrate‐Driven Approach to Determine Reactivities of α,β‐Unsaturated Carboxylic Esters Towards Asymmetric Bioreduction
Authors: Tasnádi Gábor , Winkler Christoph K. , Clay Dorina , Sultana Nargis , Fabian Walter M. F. , Hall Mélanie , Ditrich Klaus , Faber Kurt 
Published: June 2012

AbstractThe degree of CC bond activation in the asymmetric bioreduction of α,β‐unsaturated carboxylic esters by ene‐reductases was studied, and general recommendations to render these “borderline‐substrates” more reactive towards enzymatic reduction are proposed. The concept of “supported substrate activation” was developed. In general, an additional α‐halogenated substituent proved to be beneficial for enzymatic activity, whereas β‐alkyl or β‐aryl substituents were detrimental for the reactivity of nonhalogenated substrates, and α‐cyano groups showed little effect. The alcohol moiety of the ester functionality was found to have a strong influence on the reaction rate. Overall, activities were determined by both steric and electronic effects.
Controlled Synthesis of Gold Nanostars by Using a Zwitterionic Surfactant
Authors: Casu Alberto , Cabrini Elisa , Donà Alice , Falqui Andrea , Diaz‐Fernandez Yuri , Milanese Chiara , Taglietti Angelo , Pallavicini Piersandro 
Published: June 2012

AbstractBy replacing cetyltrimethylammonium bromide (CTAB) with the zwitterionic lauryl sulfobetaine (LSB) surfactant in the classical seed‐growth synthesis, monocrystalline gold nanostars (m‐NS) and pentatwinned gold asymmetric nanostars (a‐NS) were obtained instead of nanorods. The main product under all synthetic conditions was a‐NS, which have branches with high aspect ratios (AR), thus leading to LSPR absorptions in the 750–1150 nm range. The percentage of m‐NS versus a‐NS, the aspect ratio of the a‐NS branches, and consequently the position of their LSPR absorption can be finely tuned simply by regulating the concentration of reductant, the concentration of surfactant, or the concentration of the “catalytic” Ag+ cation. The m‐NS have instead shorter and larger branches, the AR of which is poorly influenced by synthetic conditions and displays an LSPR positioned around 700 nm. A growth mechanism that involves the direct contact of the sulfate moiety of LSB on the surface of the nano‐object is proposed, thereby implying preferential coating of the {111} Au faces with weak interactions. Consistent with this, we also observed the straightforward complete displacement of the LSB surfactant from the surface of the nanostars. This was obtained by the simple addition of thiols in aqueous solution to yield extremely stable coated a‐NS and m‐NS that are resistant to highly acidic, basic, and in similar to in vivo conditions.
Enhanced Magnetic Hardness in a Nanoscale Metal–Organic Hybrid Ferrimagnet
Authors: Guo Li‐Rong , Bao Song‐Song , Liu Bin , Zeng Dai , Zhao Jie , Du Jun , Zheng Li‐Min 
Published: June 2012

AbstractA new layered metal–organic hybrid compound, namely, [Co3(μ3‐OH)2(BTP)2] (1; BTP=4‐(3‐bromothienyl)phosphonate), is reported. The inorganic layer can be viewed as a pseudo‐Kagomé lattice composed of corner‐sharing irregular triangles of Co3(μ3‐OH), with the cavities filled with the PO3 groups. The interlayer space is occupied by the 3‐bromothienyl groups of BTP2−. The bulk sample of compound 1 experiences a long‐range ferromagnetic ordering below 30.5 K, with a coercivity (Hc) of 5.04 kOe at 5 K. A systematic study on the size‐dependent magnetic coercivity of 1 reveals that the coercivity of 1 increases with reduced particle size from the micrometer to the nanometer scale. When the particle size is about 50–200 nm, the coercivity reaches 24.2 kOe at 5 K. The results demonstrate that compound 1 can vary from a soft magnet to one of the hardest molecule‐based magnets, simply by reducing the particle size to nanoscale region.
Origin of Selectivity of Tsuji–Trost Allylic Alkylation of Lactones: Highly Ordered Transition States with Lithium‐Containing Enolates
Authors: Patil Mahendra , Thiel Walter 
Published: June 2012

AbstractWe report computational investigations on the mechanism and the selectivity of Pd‐catalyzed allylic alkylation of γ‐valerolactone. Density functional calculations using the B3LYP functional are performed on the selectivity‐determining nucleophilic addition step of this reaction. The B3LYP results of commonly assumed pathways fail to reproduce the observed selectivity of the reaction. Therefore, alternative pathways are considered for the nucleophilic addition step, to explain the experimentally established role of the additives LiCl and lithium diisopropyl amide (LDA) in the Pd‐catalyzed reaction. These pathways involve different approaches of the enolate toward the η3‐allylpalladium complex that are mainly guided by stabilizing Clδ−⋅⋅⋅Liδ+⋅⋅⋅O(enolate) interactions in the transition state. In the calculations, the experimentally observed trans‐product selectivity for the prototypical reaction with (S)‐BINAP ligands is found only when assuming the addition of a “mixed” Li‐enolate/LiCl adduct to the η3‐allylpalladium complex. This mechanism provides a reasonable explanation for the experimental results and sheds light on the role of LiCl in the reaction. The analysis of the different transition‐state models allows us to identify steric and electronic factors that stabilize or destabilize the relevant diastereomeric transition states. Calculations for different combinations of substrates (γ‐valerolactone and δ‐caprolactone) and catalysts (with (R)‐ and (S)‐BINAP ligands) reproduce the experimentally observed selectivities well and thus provide further support for the proposed mechanism.
CH Activation: A Complementary Tool in the Total Synthesis of Complex Natural Products
Authors: Chen David Y.‐K. , Youn So Won 
Published: June 2012

AbstractThe recent advent of transition‐metal mediated CH activation is revolutionizing the synthetic field and gradually infusing a “CH activation mind‐set” in both students and practitioners of organic synthesis. As a powerful testament of this emerging synthetic tool, applications of CH activation in the context of total synthesis of complex natural products are beginning to blossom. Herein, recently completed total syntheses showcasing creative and ingenious incorporation of CH activation as a strategic manoeuver are compared with their “non‐CH activation” counterparts, illuminating a new paradigm in strategic synthetic design.
Hot Gas Filtration in Biomass‐Based Synthesis Gas
Authors: Grove Anne Kristin , Vodegel Stefan 
Published: June 2012

AbstractBei der thermochemischen Konversion von biologischen Stoffen zu Synthesegas im Wirbelschichtreaktor gehen Nährstoffe als Staub ins Produktgas. Mit der Heißgasfiltration besteht die Möglichkeit, diese Mineralien zurückzugewinnen. Die Besonderheiten des Gases stellen neue technische Aufgaben. Der folgende Artikel schildert jahrelange Betriebs‐ und Optimierungserfahrungen in einer Technikumsanlage.
Characterization of a human βV‐tubulin antibody and expression of this isotype in normal and malignant human tissue
Authors: Chao Suzan K. , Wang Yihong , Verdier‐Pinard Pascal , Yang Chia‐Ping H. , Liu Lingling , Rodriguez‐Gabin Alicia , McDaid Hayley M. , Horwitz Susan Band 
Published: July 2012

AbstractThere are seven distinct β‐tubulin isotypes and eight α‐tubulin isotypes in mammals that are hypothesized to have tissue‐ and cell‐specific functions. There is an interest in the use of tubulin isotypes as prognostic markers of malignancy. βV‐tubulin, like βIII‐tubulin, has been implicated in malignant transformation and drug resistance, however little is known about its localization and function. Thus, we generated for the first time, a rabbit polyclonal antibody specific for human βV‐tubulin. The antibody did not cross‐react with mouse βV‐tubulin or other human β‐tubulin isotypes and specifically labeled βV‐tubulin by immunoblotting, immunofluorescence and immunohistochemistry. Immunohistochemistry of various human normal tissues revealed that βV‐tubulin was expressed in endothelial cells, myocytes and cells with muscle differentiation, structures with transport and/or secretory function such as renal tubules, pancreatic ducts and bile ducts, and epithelium with secretory function such as prostate. βV‐tubulin was also specifically expressed in pancreatic islets and intratubular germ cell neoplasia, where it may have diagnostic utility. Initial studies in breast, lung and ovarian cancers indicated aberrant expression of βV‐tubulin, suggesting that this isoform may be associated with tumorigenesis. Thus, βV‐tubulin expression is a potentially promising prognostic marker of malignancy. © 2012 Wiley Periodicals, Inc
Ground‐State and Excitation Spectra of a Strongly Correlated Lattice by the Coupled Cluster Method
Authors: Mirone Alessandro 
Published: June 2012

AbstractThe coupled cluster method is applied to a strongly correlated lattice Hamiltonian, and the coupled cluster linear response method is extended to the calculation of electronic spectra by finding an approximation to a resolvent operator which describes the spectral response of the coupled cluster solution to excitation operators. In this spectral coupled cluster method, the ground and excited states appear as resonances in the spectra, and the resolvent can be iteratively improved in selected spectral regions. The method is applied to a MnO2 plane model which corresponds to previous experimental works.