bluuebunny/crossref_metadata_2025_split huggingface dataset:
1,3,5‐Triazine‐Based Synthons in Supramolecular Chemistry
Authors: Gamez Patrick , Reedijk Jan 
Published: October 2005

AbstractInterest in supramolecular chemistry has grown significantly during the past two decades. In this context, hydrogen bonding and/or coordinative interactions have been extensively used to generate self‐assembled one‐, two‐ or three‐dimensional polymeric networks. Crystal structure prediction has progressed tremendously, and the challenge for the contemporary supramolecular chemist is now to produce custom‐made functional (and multifunctional) materials involving intermolecular interactions. Since the early 1990s, 1,3,5‐triazine derivatives have shown their potential as building blocks for the preparation of such materials. In this microreview, a selection of outstanding examples of supramolecular networks involving the 1,3,5‐triazine unit are discussed, illustrating the possibility of forming remarkable architectures by means of coordination and/or hydrogen bonds and their applications in host–guest chemistry, catalysis, anion recognition, sensoring, electronics and magnetism. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
A Selective Direct Aldol Reaction in Aqueous Media Catalyzed byZinc–Proline
Authors: Fernandez‐Lopez Ruben , Kofoed Jacob , Machuqueiro Miguel , Darbre Tamis 
Published: October 2005

AbstractThe Zn–proline complex is shown to catalyze the aldol reaction of acetone and a wide range of arenecarbaldehydes in aqueous media, accepting even deactivated arenecarbaldehydes such as methoxybenzaldehydes in good yields. Enantiomeric excesses of up to 56 % could be obtained with 5 mol‐% of the catalyst at room temperature, and up to 66 % at –15 °C. The aldol reaction is regio‐ and stereoselective with hydroxyacetone (moderate yields) and dihydroxyacetone (excellent donor, 80–90 % yields with 5 mmol‐equiv.). Plausible mechanisms for the reaction are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
A Photoswitchable Rotaxane with an Unfolded Molecular Thread
Authors: Schmidt‐Schäffer Sebastian , Grubert Lutz , Grummt Ulrich W. , Buck Karin , Abraham Werner 
Published: October 2005

AbstractNovel [2]rotaxanes containing the tetracationic cyclophane cyclobis(paraquat‐4,4‐biphenylene) and a dumbbell‐shaped molecular thread incorporating a photoactive diarylcycloheptatriene station as well as a photo‐inactive aryl station have been synthesized with yields of nearly 30% by the coupling of two halves of the molecular thread. Each half incorporates one of the two stations which are recognized by the tetracationic ring. The switch principle is based on photoheterolysis of a diarylcycloheptatriene bearing a suitable leaving group such as a methoxy substituent. The rotaxanes were transformed into the related rotaxanes incorporating a diaryl tropylium unit by electrochemical oxidation. The co‐conformation of all rotaxanes was determined by 1H NMR and UV/Vis spectroscopy. It has been shown that the occupation of the two different stations by the tetracationic ring depends both on the electron donor capacity of these stations and on the chain units between the stations. The desired preferred occupation of the diarylcycloheptatriene station was achieved by fine tuning both the stopper group at the end of the molecular thread and the number of oxygen atoms within the chain. By tuning the chain length it has also been achieved that both of the rotaxanes incorporating the diarylcycloheptatriene unit and the tropylium‐containing rotaxanes adopt an unfolded structure in solution. The tetracationic ring resides exclusively on the second aryl station within the tropylium rotaxanes. Switching between co‐conformations of the cycloheptatrienyl‐containing rotaxanes and the tropylium‐containing rotaxanes can be achieved by photoheterolysis of the methoxy‐substituted diarylcycloheptatriene, yielding the tropylium rotaxane, which reacts thermally back to the cycloheptatriene rotaxane, and thus closes the switching cycle. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Syntheses, Structures and Electronic Properties of Cationic Hydroxy‐ and Methoxy‐Substituted Tricarbonyl(tetracyclopropylcyclopentadienyl)iron Complexes
Authors: Emme Ingo , Labahn Thomas , de Meijere Armin 
Published: October 2005

AbstractTetracyclopropylcyclopentadienone, upon liberation from its previously known tricarbonyliron complex 3, undergoes rapid [4+2] cyclodimerization to the highly congested1,2,4,5,6,7,8,9‐octacyclopropyltricyclo[5.2.1.02,6]deca‐4,8‐diene‐3,10‐dione (6) which was characterized by an X‐ray crystal structure analysis. Upon alkylation of 3 with Me3OBF4 as well as protonation with HBF4 or CF3SO3H, the remarkably stable cationic tricarbonyl(tetracyclopropylcyclopentadienyl)iron complexes 9, 10 and 11, 12, respectively, were obtained in high yields (91, 87 and 74, 79 %, respectively). X‐ray crystal structural data for 11 and 12 as well as NMR‐ and IR spectroscopic evidences for all four new complexes 9–12 indicate that their positive charge predominantly rest on the tricarbonyliron fragments. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Stereoselective Synthesis of 3‐Deoxy‐4‐S‐(1→4)‐Thiodisaccharides and Their Inhibitory Activities Towards β‐Glycoside Hydrolases
Authors: Uhrig María Laura , Manzano Verónica Elena , Varela Oscar 
Published: October 2005

AbstractThe sulfur linkage of β‐(1→4)‐thiodisaccharides was constructed with excellent diastereoselectivity by Michael addition of 2,3,4,6‐tetra‐O‐acetyl‐1‐thio‐β‐D‐galactose (2) or its β‐D‐glucose isomer (3) to sugar‐derived (2S, 6S)‐6‐acetoxymethyl‐2‐(2‐propyloxy)‐2H‐pyran‐3(6H)‐one (1). These reactions led to the per‐O‐acetyl glycosides of 3‐deoxy‐4‐S‐glycopyranosyl‐4‐thiohexopyranosid‐2‐ulose (4 and 5, respectively). Similar conjugated addition to the enone 1 of the isothiouronium salts 6 or 7, precursors in the synthesis of 2 or 3, also afforded the thiodisaccharides 4 or 5, respectively, with exclusive formation of the isomer that has an R configuration for the C‐4 stereocenter of the reducing‐end. The carbonyl function of 4 and 5 was reduced, and the resulting products were O‐deacetylated to give the free 4‐S(1→4)‐thiodisaccharides 10, 11, 14, and 15, which have a deoxy functionality adjacent to the thio group. These compounds were tested as inhibitors of glycoside hydrolases. Thus 11, the 3‐deoxy‐4‐thiomimetic of Galβ(1→4)Gal, proved to be a competitive inhibitor of the β‐galactosidase from E. coli (Ki = 0.16 mM). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
CuI‐Catalyzed Alkyne–Azide “Click” Cycloadditions from a Mechanistic and Synthetic Perspective
Authors: Bock Victoria D. , Hiemstra Henk , van Maarseveen Jan H. 
Published: October 2005

AbstractCuI‐catalyzed alkyne–azide cycloaddition provides 1,4‐disubstituted 1,2,3‐triazoles with such efficiency and scope that the transformation has been described as “click” chemistry. An overview of the mechanism of this remarkable reaction is presented as a means to explain the myriad of experimental results, particularly the various methods of catalyst generation, solvent and substrate effects, and choice of base or ligand. Both solution‐phase and solid‐phase results are comprehensively examined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Silanediol Protease Inhibitors: From Conception to Validation
Authors: Sieburth Scott McN. , Chen Chien‐An 
Published: October 2005

AbstractSilanediols are isosteric with the unstable hydrated carbonyl group, but are most commonly associated with polymerization to give silicone polymers. Placement of a silanediol in a dipeptide analogue yields a new kind of nonhydrolyzable transition‐state‐analogue protease inhibitor. Both metallo and aspartic protease inhibitors have been prepared using silanediols, with enzyme inhibition in the low nanomolar range. Structure–activity comparisons with known inhibitors, efficacy in whole cell assays, and a crystal structure of a silanediol inhibitor bound to the thermolysin active site establish these silanediol inhibitors as effective and predictable new protease inhibitor tools. Recent chemistry developments have led to efficient and streamlined preparation of these inhibitors. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
GaCl3 in Organic Synthesis
Authors: Amemiya Ryo , Yamaguchi Masahiko 
Published: October 2005

AbstractGaCl3 and organogallium compounds generated from GaCl3 possess novel properties that can be used in organic synthesis. This microreview summarizes our studies on the use of GaCl3 as 1) a reagent to generate organogallium compounds, which can carbometalate unactivated unsaturated bonds, and 2) a Lewis acid which can activate organic molecules by interacting with the π‐, n‐, and σ‐electrons. Carbometalation of carbon–carbon triple bonds (carbogallation) is a characteristic reaction of organogallium compounds. Carbogallation of gallioacetylenes occurs at lower temperatures than with silylacetylenes, and addition to 1‐alkynes is slow. The regiochemistry and stereochemistry are in accordance with other carbometalation reactions, giving 1,1‐digallio or 1‐gallio‐1‐silyl intermediates in the cis‐addition mode. Carbogallation of enolates and acetylenes is effective for the α‐ethenylation of ketones, and a catalytic version of the reaction has been developed. When chloroacetylenes are used, α‐ethynylation of ketones proceeds by addition and β‐elimination. Aniline and phenols can be ethenylated or ethynylated at the o‐position of the heteroatom groups. GaCl3 has been used not only for the ethynylation of heteroatom compounds but also hydrocarbons such as 1,4‐enynes or 1,4‐diynes by C–H activation, and triethynylvinylmethanes and tetraethynylmethanes are obtained in one step via nucleophilic propargylgallium intermediates. As a Lewis acid, GaCl3 has the ability to interact with π‐acids such as silylacetylenes. The resulting gallium complexes are sufficiently electrophilic to react with aromatic hydrocarbons, even at –78 °C, to give an organogallium arenium intermediate. Arenium cations or vinyl cations appear to be stabilized in the presence of GaCl3. An unusual orientation has been observed in electrophilic aromatic substitution with GaCl3. GaCl3 activates even cycloalkane C–H bonds at σ‐electrons, and the reaction of cis‐perhydronaphthalene and naphthalene catalytically gives 2‐naphthylated trans‐perhydronaphthalene. Two C–H activation reactions of hydrocarbons with GaCl3 are notable as they generatenucleophilic and electrophilic species. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
The Phospha‐Michael Addition in Organic Synthesis
Authors: Enders Dieter , Saint‐Dizier Alexandre , Lannou Marie‐Isabelle , Lenzen Achim 
Published: October 2005

AbstractPhosphorus is essential for many reagents in organic synthesis, for ligands of late‐transition metals and for phosphono‐ and phosphanylamino acids, the latter being important isosteres of amino acids. Similar to the Michaelis–Arbuzov and the Michaelis–Becker reaction the phospha‐Michael addition, i. e. the addition of a phosphorus nucleophile to an acceptor‐substituted alkene or alkyne, certainly represents one of the most versatile and powerful tools for the formation of P–C bonds since many different electrophiles and P nucleophiles can be combined with each other. This offers the possibility to access many diversely functionalised products. With this article, we try to give an instructive overview of this reaction. The outline of this review is supposed to be rather general and it is its goal to make the reader familiar with reactivity principles which are common to the different classes of electrophiles and/or P nucleophiles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Studies on the Synthesis of Apoptolidin: Progress on the Stereocontrolled Assembly of the Pseudo Aglycone of Apoptolidin
Authors: Wu Bin , Liu Qingsong , Jin Bohan , Qu Tao , Sulikowski Gary A. 
Published: October 2005

AbstractProgress on a stereocontrolled total synthesis of the pseudo aglycone of apoptolidin (2) starting from (S)‐epichlorohydrin is reported. The lower C(12)–C(28) fragment (4) was derived by consecutive stereoselective aldol reactions and extended using a Suzuki cross‐coupling reaction. Studies on glycoyslation of the C9 hydroxy group are also described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Regioselective Synthesis of Novel e‐Edge‐[60]fullerenylmethanodihydropyrroles and 1,2‐Dihydromethano[60]fullerenes
Authors: Chaker Leila , Ball Graham E. , Williams James R. , Burley Glenn A. , Hawkins Bill C. , Keller Paul A. , Pyne Stephen G. 
Published: October 2005

AbstractTreatment of a tethered N‐(diphenylmethylene)glycinate‐malonate derivative with [60]fullerene under Bingel conditions yielded an e‐edge‐[60]fullerenylmethanodihydropyrrole adduct in a regioselective manner. The regiochemical outcome was independent of the order of addition of either the N‐(diphenylmethylene)glycinate or the malonate moieties. This new bis‐adduct was also prepared in 13C‐enriched form allowing for its unequivocal structural characterization by 2D INADEQUATE NMR experiments. Ring opening of the dihydropyrrole functionality of the bis‐adducts under reductive conditions gave exclusively novel dihydromethano[60]fullerene derivatives. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Carbonate melting and peperite formation at the intrusive contact between large mafic dykes and clastic sediments of the upper Palaeozoic Saint‐Jules Formation, New‐Carlisle, Quebec
Authors: Jutras P. , Macrae A. , Owen J. V. , Dostal J. , Préda M. , Prichonnet G. 
Published: October 2005

AbstractThe base of an upper Palaeozoic graben‐fill in eastern Canada was affected by mafic dyke intrusions shortly after deposition, resulting in the formation of peperite. Complex magma–sediment interactions occurred as the melts mingled with the wet and poorly consolidated clastic material of this sedimentary basin, which is separated from underlying rocks by the Acadian unconformity (Middle Devonian). As a result of these interactions, the mafic rocks are strongly oxidized, albitized and autobrecciated near and above the unconformity, where blocky juvenile clasts of mafic glass and porphyritic basalt have mingled with molten or fluidized sediments of the upper Palaeozoic Saint‐Jules Formation, forming a peperite zone several metres thick. In contrast to most peperite occurrences, the New‐Carlisle peperites are associated with the tip of dykes rather than with the sides of sills or dykes. We argue that more heat can be concentrated above a dyke than above a sill, as the former provides a more efficient and focused pathway for heated waters to invade the poorly consolidated host sediments. Superheated groundwaters that issued from the sides of the dykes appear to have promoted melting of carbonate components in calcareous sedimentary rock clasts of the Saint‐Jules Formation, locally generating carbonate melts that contributed to the mingling of juvenile and sedimentary clasts in the peperite. Copyright © 2005 John Wiley & Sons, Ltd.
High‐pressure mineral assemblage in granitic rocks from continental units, Alpine Corsica, France
Authors: Malasoma Alessandro , Marroni Michele , Musumeci Giovanni , Pandolfi Luca 
Published: October 2005

AbstractThe Popolasca–Francardo area of northern Corsica contains an assemblage of continental tectonic units affected by an Alpine deformation. In one of these units, Unit II, previously regarded as weakly metamorphosed, a metamorphic mineral assemblage characterized by sodic amphibole, phengite, quartz, albite and epidote has been found in an aplite dyke that cuts the dominant granitoids. Peak‐metamorphic temperature and pressure conditions of 300–370°C and 0.50–0.80 GPa, respectively, have been determined. This finding indicates that a continuous belt of continental slices, characterized by high‐pressure, low‐temperature metamorphism of Tertiary age, extends from the Tenda Massif in the north to the Corte area in the south, thus placing additional constraints on the tectonic evolution of Alpine Corsica. Copyright © 2005 John Wiley & Sons, Ltd.
Hydrodynamic compression of young and adult rat osteoblast‐like cells on titanium fiber mesh
Authors: Walboomers X. F. , Elder S. E. , Bumgardner J. D. , Jansen J. A. 
Published: October 2005

AbstractLiving bone cells are responsive to mechanical loading. Consequently, numerous in vitro models have been developed to examine the application of loading to cells. However, not all systems are suitable for the fibrous and porous three‐dimensional materials, which are preferable for tissue repair purposes, or for the production of tissue engineering scaffolds. For three‐dimensional applications, mechanical loading of cells with either fluid flow systems or hydrodynamic pressure systems has to be considered. Here, we aimed to evaluate the response of osteoblast‐like cells to hydrodynamic compression, while growing in a three‐dimensional titanium fiber mesh scaffolding material. For this purpose, a custom hydrodynamic compression chamber was built. Bone marrow cells were obtained from the femora of young (12‐day‐old) or old (1‐year‐old) rats, and precultured in the presence of dexamethasone and β‐glycerophosphate to achieve an osteoblast‐like phenotype. Subsequently, cells were seeded onto the titanium mesh scaffolds, and subjected to hydrodynamic pressure, alternating between 0.3 to 5.0 MPa at 1 Hz, at 15‐min intervals for a total of 60 min per day for up to 3 days. After pressurization, cell viability was checked. Afterward, DNA levels, alkaline phosphatase (ALP) activity, and extracellular calcium content were measured. Finally, all specimens were observed with scanning electron microscopy. Cell viability studies showed that the applied pressure was not harmful to the cells. Furthermore, we found that cells were able to detect the compression forces, because we did see evident effects on the cell numbers of the cells derived from old animals. However, there were no other changes in the cells under pressure. Finally, it was also noticeable that cells from old animals did not express ALP activity, but did show similar calcified extracellular matrix formation to the cells from young animals. In conclusion, the difference in DNA levels as reaction toward pressure, and the difference in ALP levels, suggest that the osteogenic properties of bone marrow‐derived osteoblast‐like cells are different with respect to the age of the donor. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Surface‐attached PEO in the form of activated pluronic with immobilized factor H reduces both coagulation and complement activation in a whole‐blood model
Authors: Andersson Jonas , Bexborn Fredrik , Klinth Jeanna , Nilsson Bo , Ekdahl Kristina Nilsson 
Published: October 2005

AbstractIn the present work we have bound Pluronic™, a class of triblock copolymers consisting of a block of polypropylene oxide (PPO) surrounded on each side by polyethylene oxide (PEO) blocks, to polystyrene surfaces and investigated the thrombogenicity and complement activation of this construct upon exposure to whole blood. The surface was highly inert towards coagulation, unfortunately at the expense of increased complement activation. We, therefore, as an alternative approach, used End‐Group Activated Pluronic to conjugate factor H, a regulator of complement activation (RCA), to the surface. The bound factor H did not detach from the surface upon incubation with human serum. Furthermore, factor H bound in a physiological conformation could to a significant degree attenuate complement activation at the Pluronic™ surface. Thus, we have created a hybrid surface in which the coagulation‐inert properties of the original Pluronic™ are supplemented with a specific complement‐inhibitory effect. Medical device technology includes numerous potential applications for crosslinkers that are capable of specifically binding biomolecules to surfaces with retained activity. These applications include coupling of functional biomolecules to biomedical devices such as stents and grafts. The biomolecule may be an RCA, antibody, or other beneficial ligand. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
A promoter element of the CD‐RAP gene is required for repression of gene expression in non‐cartilage tissues in vitro and in vivo
Authors: Okazaki Ken , Yu Hua , Davies Sherri R. , Imamura Toshihiro , Sandell Linda J. 
Published: October 2005

AbstractThe cartilage‐derived retinoic acid‐sensitive protein (CD‐RAP) gene is expressed predominately in cartilage. Previous studies in transgenic mice have shown that the DNA promoter segment from −2,251 bp to −2,068 bp of the CD‐RAP gene contains elements critical for gene expression. Subsequent studies revealed both positive and negative regulatory motifs in this 183 bp element. Here we show that this element demonstrates activation or repression of gene expression in vitro and in vivo based on cell type and content of transcription factors. The distribution of Sox (positive) and C/EBP (negative) transcription factors in cell lines and in mouse tissues is consistent with their positive and negative roles. In transgenic mice, when the 183‐bp element was removed from a 3,345‐bp cartilage‐specific CD‐RAP promoter, expression of the reporter gene became widespread, being observed in muscle, bone, lung, and liver in addition to cartilage. In vitro, mutation of the C/EBP site activated the inactive 3,345‐bp CD‐RAP gene promoter in myoblastic cells, suggesting that this site is responsible for (−2,079 bp) repression. These results indicate that the 183‐bp element plays an important role in cartilage‐specific gene expression by acting as a chondrocyte‐regulatory module repressing transcription in non‐chondrocytes and contributing to activation in chondrocytes. This is the first report of a functional DNA element necessary for repression in non‐cartilage tissues in vivo. J. Cell. Biochem. 97: 857–868, 2006. © 2005 Wiley‐Liss, Inc.
SCN− binding to the charged lysines of histones end domains mimics acetylation and shows the major histone–DNA interactions involved in eu and heterochromatin stabilization
Authors: Patrone Eligio , Coradeghini Rosella , Barboro Paola , D'Arrigo Cristina , Mormino Michele , Parodi Silvio , Balbi Cecilia 
Published: October 2005

AbstractSCN− binds to the charged amino group of lysines, inducing local changes in the electrostatic free energy of histones. We exploited this property to selectively perturb the histone–DNA interactions involved in the stabilization of eu and heterochromatin. Differential scanning calorimetry (DSC) was used as leading technique in combination with trypsin digestion that selectively cleaves the histone end domains. Euchromatin undergoes progressive destabilization with increasing KSCN concentration from 0 to 0.3 M. Trypsin digestion in the presence of 0.2 M KSCN show that the stability of the linker decreases as a consequence of the competitive binding of SCN− to the amino groups located in the C and N‐terminal domain of H1 and H3, respectively; likewise, the release of the N‐terminal domain of H4 induces an appreciable depression in both the temperature and enthalpy of melting of core particle DNA. Unfolding of heterochromatin requires, in addition to further cleavage of H4, extensive digestion of H2A and H2B, strongly suggesting that these histones stabilize the higher order structure by forming a protein network which extends throughout the heterochromatin domain. J. Cell. Biochem. 97: 869–881, 2006. © 2005 Wiley‐Liss, Inc.