bluuebunny/crossref_metadata_2025 huggingface dataset:
Tris(trimethylsilyl)silanides of the Heavier Alkali Metals—A Structural Study
Authors: Klinkhammer Karl W.
Published: July 2007

Transmetalation reactions between bis(hypersilyl)zinc Zn[Si(SiMe3)3]2 and alkali metals have already been established as a facile route to powders of the solvent‐free potassium, rubidium, and cesium derivatives of tris(trimethylsilyl)‐silane (hypersilane, (Me3Si)3SiH).[1,2] By the use of boiling n‐heptane as the solvent, the hitherto unknown NaSi(SiMe3)3 (1) along with the previously synthesized KSi(SiMe3)3 (2) have now been obtained as colorless crystalline materials. Information from NMR and Raman spectra in conjunction with the acute Si‐Si‐Si angles found in their molecular structures indicate mainly ionic bonding. This was verified by population analyses of suitable model systems. Both hypersilanides[2] consist of cyclic dimers [MSi(SiMe3)3]2 (1a, M = Na; 2a, M = K) with almost planar M2Si2 rings (Na‐Si = 299 pm (av); K‐Si = 339 pm (av)), which are linked up into coordination polymers. In a similar manner to the related rubidium and cesium derivatives, a pentane suspension of the potassium compound afforded a yellow solution on addition of benzene, from which the crystalline, bright yellow tris(benzene) solvate 2·(benzene)3 (2b) was isolated. Complex 2b consists of monomers containing short K‐Si bonds (332–334 pm) and three η6‐bonded benzene molecules. No solvate of 1 was obtained under these conditions. However, on crystallization from pure benzene, crystals of (1)2·benzene (1b) were isolated (Na‐Si = 302 pm (av)). Benzene was found to be intercalated between rods of coordination polymers of (1)2. In addition, the influence of π or s̀ donors on the molecular and crystal structures of hypersilylrubidium (3) and cesium (4) was investigated. The structures of the tetrahydrofuran solvate (4)2·THF (4c), the biphenylene/pentane complex (4)2·biphen·(pentane)0.5 (4b) along with the known toluene solvates (3)27dot;toluene (3a) and (4)2·(toluene)3 (4a)[1a] are compared. Finally, an example is presented of how the alkali metal hypersilanides could be utilized in preparing extremely bulky stannanide anions.
Reactivity of Coordinatively Unsaturated Trivalent Chromium Complexes with Sulfur: Preparation of Novel Sulfide‐bridged Dinuclear CrIV Derivatives
Authors: Reardon Damien , Kovacs Istvan , Ruppa Kamalesh B. P. , Feghali Khalil , Gambarotta Sandro , Petersen Jeffrey
Published: July 2007

The homoleptic CrIII amide complexes [(RR′N)3Cr] [R = R′ = cyclohexyl (1a); R = adamantyl, R′ = 3,5‐Me2Ph (1 b)] were prepared and characterized. Reactions with elemental sulfur produced the corresponding dinuclear complexes [{(RR′N)2Cr}2(μ‐S)2] (2) through loss of one amide group. These two new dinuclear CrIV species are paramagnetic with magnetic moments lower than expected for the d2 electronic configuration of CrIV. Magnetic measurements and ab initio calculations were carried out to elucidate the nature of magnetic interactions in these dinuclear systems. The molecular structures of 1a and 2a were elucidated by X‐ray crystal structures.
Electrospray Mass Spectrometry of Poly(propylene imine) Dendrimers—The Issue of Dendritic Purity or Polydispersity
Authors: Hummelen Jan C. , Van Dongen Joost L. J. , Meijer E. W.
Published: July 2007

Electrospray mass spectrometry (ESI‐MS) is used to analyze in detail the structure of the first five generations of the poly(propylene imine) dendrimers with 4–64 end groups. Although the reaction sequence to prepare these dendrimers is highly optimized, an accumulation of statistical defects is observed at higher generations. A simple statistical simulation allows the assignment of all peaks in the deconvoluted spectrum and the determination of yields for each side reaction in the formation of each generation. The fifth generation of the poly(propylene imine) dendrimer containing amine end groups, which is formed after 248 consecutive reaction steps, possesses a dendritic purity of approx. 20%, which corresponds to a polydispersity of approximately 1.002. The defects in the divergent growth patterns of dendrimers are compared to those observed in the Merrifield synthesis of polypeptides.
Reaction of „Jordan′s Cation”︁ [Cp2ZrCH3(thf)]+ with Amino Acid‐Derived Isocyanates—A First Synthetic Route to Oligopeptide‐Modified Group 4 Bent Metallocene Cation Systems
Authors: Oberhoff Markus , Erker Gerhard , Fröhlich Roland
Published: July 2007

The organometallic cation [Cp2ZrCH3(thf)]+, employed as the tetraphenylborate salt (1), reacts cleanly in 1:1 stoichiometry with the isocyanates 2 derived from valine methyl ester or valylvaline methyl ester, respectively. In each case addition of the Zr–CH3 group to the isocyanate sp‐carbon center is observed with formation of a functionalized zirconocene cation derivative containing a chelating N‐metallated N‐acetylvaline methyl ester (3a) or N‐acetylvalylvaline methyl ester (3b) moiety, respectively, coordinated in the bent metallocene s̀‐ligand plane. The spectroscopic data of 3, supported by an X‐ray crystal structure analysis of the zirconated dipeptide derivative 3b, have revealed the presence of chelating (η1‐O:η1‐N)‐coordination of the terminal N‐acetyl groups in addition to a Zr–O=C interaction with the adjacent valyl amido group.
Complex Formation of the Antiviral 9‐[2‐(Phosphonomethoxy)Ethyl]Adenine (PMEA) and of Its N 1, N 3, and N 7 Deaza Derivatives with Copper(II) in Aqueous Solution
Authors: Blindauer Claudia A. , Emwas Abdul H. , Holý Antonín , Dvořáková Hana , Sletten Einar , Sigel Helmut
Published: July 2007

The stability constants of the 1:1 complexes formed between Cu2+ and the anions of the N 1, N 3, and N 7 deaza derivatives of 9‐[2‐(phosphonomethoxy)‐ethyl]adenine (PA2‐), Cu(H;PA)+ and Cu(PA), were determined by potentiometric pH titration in aqueous solution (25 °C; I = 0.1 M, NaNO3) and compared with previous results for 9‐[2‐(phosphonomethoxy)ethyl]adenine (PMEA2‐) and (phosphonomethoxy)ethane (PME2‐). A microconstant scheme reveals that in Cu(H;PA)+ Cu2+ is coordinated to the nucleobase, H+ being at the phosphonate group, in about 90% of the Cu(H;PMEA)+ and Cu(H;1‐deaza‐PMEA)+ species, but only in about 37% and 12% of the corresponding complexes with H(3‐deaza‐PMEA)‐ and H(7‐deaza‐PMEA)‐, respectively. Straight‐line plots of log KCuCu(R–PO3) versus pKHH(R–PO3) for simple phosph(on)ate ligands show that all the Cu(PA) complexes, including those with PMEA2‐ and PME2‐, are more stable than expected simply from the basicity of the ‐PO2‐ group; to some extent five‐membered chelates (Cu(PA)cl/O) involving the ether oxygen of the ‐CH2–O–CH2–PO2‐3 chain are formed, and in all complexes an additional nucleobase–metal‐ion interaction occurs. Based on 1H NMR line‐broadening measurements and structural considerations it is concluded that in Cu(3‐deaza‐PMEA) the interaction occurs with N7 whereas in Cu(7‐deaza‐PMEA), Cu(1‐deaza‐PMEA), and Cu(PMEA) it occurs with N3. The proof of a metal ion–N3 interaction is important (and also of relevance regarding DNA) because so far this interaction has received little attention. In all Cu(PA) systems three major isomeric species are in equilibrium; for example, 17(∓3)% of Cu(PMEA) exists as an isomer with a sole Cu2+–phosphonate coordination, 34(∓10)% as Cu(PMEA)cl/O, and in 49(∓10)% the Cu2+ is bound to the phosphonate group, the ether O, and N3. In contrast, 54(∓8)% of Cu(5′‐AMP) occurs as an isomer with sole Cu2+–phosphate coordination and 46(∓8)% as a macrochelate involving N7 too.
Chirality in Dendritic Architectures
Authors: Peerlings H. W. I. , Meijer E. W.
Published: July 2007

At first glance the topic of chiral dendrimers seems to be a contradiction in terms. However, recent studies reveal that both the building blocks of the dendrimer and the overall dendritic architecture can be chiral and that chirality can be introduced at various levels. The expression of optical activity in these enantiomerically pure dendrimers as a result of conformational (dis)order has proven to be of special interest. In this Concepts article we present the different approaches to introducing chirality in dendritic architectures, organized through their possible impact in fields such as biocompatibility, catalysis, molecular recognition, and surface chemistry. Also, the relation between molecular chirality of core or building block and the macroscopic chirality of dendritic objects is discussed.
Development of Tools for the Design of Selectin Antagonists
Authors: Kolb Hartmuth C. , Ernst Beat
Published: July 2007

A molecular modeling tool for the rational design of E‐selectin antagonists based on the lead structure sialyl Lewisx has been developed. The binding affinity to the receptor is considerably influenced by the entropy and consequently by the antagonist's ability to place its pharmacophores in an optimal spatial arrangement, i.e., by its preorganization for binding. The computational model assesses the preorganization of a potential selectin antagonist with the aid of Monte Carlo (jumping between wells)/stochastic dynamics [MC(JBW)/SD] simulations. The model has been validated by correlating preorganization and bioactivity of several selectin antagonists. The results suggest that only preorganized compounds are likely to bind to E‐selectin.
The Versatility of Lithium Reagents in Synthetic Organometallic Chemistry: Their differing reactions with [Cp*Mo(NO)(CH2SiMe3)2]
Authors: Legzdins Peter , Sayers Stephen F.
Published: July 2007

[Cp*Mo(NO)(CH2SiMe3)2] exhibits three principal types of reaction with the various lithium reagents investigated during this study, namely: regioselective deprotonation, reduction, and addition. Deprotonation of the reactant, achieved by treatment with lithium amide reagents, leads ultimately to the formation of the alkylidene „ate”︁ complex [Cp*Mo(NO)(CH2SiMe3)2(CHSiMe3)]2‐[Li2(thf)3] (1). While LiN(SiMe3)2 effects this conversion directly with no detectable intermediates, reaction with 1 equiv of LDA in THF for 15 min deprotonates the Cp* ligand to form the lithium salt of the „tucked‐in”︁ ate complex [(η5,η1‐C5Me4CH2)Mo(NO)(CH2SiMe3)2]‐[Li(thf)3] (2) in 40% isolated yield. Complex 2 slowly converts to the thermodynamically more stable 1 when left as a THF or C6D6 solution at ambient temperature for 48 h. Reaction of the dialkyl starting material with either tBuLi or PhLi leads to the production of the alkylidene complex 1 in irreproducible yields (10–50% NMR; not isolable). A kinetic analysis of the reaction of [Cp*Mo(NO)(CH2SiMe3)2] with LiN(SiMe3)2 indicated that the reaction was first‐order in both the lithium and molybdenum reagents, and the activation parameters of ΔH* = 7.3∓1.0 kcal mol−1 and ΔS* = − 34∓3 e.u. suggest an associative process. Treatment of the neutral dialkyl with 1 equiv of LiPPh2 in THF results in a one‐electron reduction and production of {[Cp*Mo(NO)(CH2SiMe3)2[Li2(thf)3] (3). If left in solution, the 17e− dialkyl anion 3 is converted to the 18e− alkylidene anion 1 by the Ph2P–PPh2 coproduct, which effects the requisite hydrogen‐atom abstraction. Finally, addition of a sterically undemanding alkyllithium reagent such as MeLi to the 16e− dialkyl reactant leads to the formation of the 18e− trialkyl anionic complex [[Cp*Mo(NO)(CH2SiMe3)2(CHSiMe3)]2‐[Li2(thf)3](Me)][Li(thf)3] (4). Warming of 4 in a C6D6 solution results in loss of methane and production of 1. In most cases, the chemistry exhibited by the Mo system is duplicated by the analogous W congener, [Cp*Mo(NO)(CH2SiMe3)2(CHSiMe3)]2‐[Li2(thf)3]. The solid‐state molecular structures of complexes 1 and 4 have been established by single‐crystal X‐ray crystallographic analyses.
The Comparative Solvatochromism of Arylazo and Heteroarylazo Compounds Based On N,N‐Diethyl‐m‐acetylaminoaniline and N,N‐Diethyl‐m‐toluidine
Authors: Hutchings Michael G. , Gregory Peter , Campbell James S. , Strong Andrew , Zamy Jean‐Paul , Lepre Anne , Mills Andrew
Published: July 2007

Azobenzene dyes derived from various anilines and aminothiaheterocycles azo‐coupled with commercially important N,N‐diethyl‐m‐toluidine (T series) and N,N‐diethyl‐m‐acetylaminoani‐line (A series) are positively solva‐tochromic. The visible spectra of 16 pairs of derivatives have been measured in up to 22 solvents, and the transition energies related to Kamlet‐Taft solvent polarity parameters. In general, A‐series dyes are more bathochromic than their T‐series counterparts in nonpolar solvents, consistent with colour chemistry tradition. However, in more dipolar solvents the more bathochromic T‐series representatives unexpectedly become more bathochromic than their A‐series partners. The relative solvatochromic shifts of the A and T series are related to their respective dipole moments. These in turn are distinguished by the effect of the anilide carbonyl group dipole moment, which is antiparallel to, and thus reduces, the dipole moment of the chromogen.
Proof of Inversion of Configuration on Stannylation of a Configurationally Stable, Tertiary Benzyllithium Compound from a Single‐Crystal X‐Ray Structure Analysis
Authors: Hammerschmidt F. , Hanninger A. , Völlenke H.
Published: July 2007

Configurationally stable, dipole‐stabilised benzyllithium compounds (R)‐and (S)‐1 b, prepared by deprotonation of the corresponding esters with sBuLi in toluene/di‐ethyl ether (5:1), reacted with (–)‐menthyldimethyltin bromide to afford the stannanes (–)‐3 and ( + )‐4, respectively. A single‐crystal X‐ray structure analysis of compound (–)‐3 proved that stannylation occurred with inversion of the configuration at the benzylic centre, assuming retention for the deprotonation step. Lithio‐destannylation and deuteration with MeOD follow a retentive course.
The Quest For Extra‐Large Pore, Crystalline Molecular Sieves
Authors: Davis Mark E.
Published: July 2007

The definition and reasons for desiring extralarge pore, crystalline molecular sieves are ennumerated. A historical perspective on the development of these materials is presented with emphasis on critical features important for practical application. Based on the known physiochemical properties of extra‐large pore materials, several avenues for their synthesis are suggested. Finally, a few issues of concern when dealing with this class of materials are presented.
Gold Clusters and Colloids in Alumina Nanotubes
Authors: Hornyak Gabor , Kröll Michael , Pugin Raphael , Sawitowski Thomas , Schmid Günter , Bovin Jan‐Olov , Karsson Gunnel , Hofmeister Herbert , Hopfe Sigrid
Published: July 2007

The fabrication of a supported and insulated quantum wire would be of great interest, especially if electronic information could be accessed to determine charging and conductivity profiles. The feasibility of forming one‐dimensional configurations of ≈ 15 nm gold colloids and 1.4 nm gold clusters via template methods of synthesis has now been demonstrated. The template host material consisted of porous alumina membranes formed by an electrochemical anodic process. The pores of the membrane, and hence the parallel pore channels, were packed in a hexagonal array. Alumina membranes are excellent template materials because of their high degree of order, thermal and chemical stability, and optical clarity. Pore diameter was controlled by regulation of the applied anodic potential (ca. 1.4 nm V‐1). The pore channels were filled by one of three methods: vacuum induction (colloids only), electrophoresis (clusters only), or immersion (clusters, which were then converted into colloids by heating). Rudimentary wires consisting of colloids and clusters were successfully formed. In both cases, the diameter of the pore channel exceeded that of the clusters or colloids. The wires thus formed conformed to the pore channel by forming helical secondary structures. It was not possible to form contiguous wires of clusters by immersion, or of colloids formed from clusters after heating. Composites (consisting of the gold‐alumina system) were a bright scarlet color with an absorption maximum (λmax) at 519.5 nm. This is an unexpected result for spherical and small‐diameter (10 nm) gold colloids, which normally absorb at λmax 525–530 nm, a ruby‐red color. Possible causes of this small but remarkable blue shift are discussed below. A new Au55 cluster ligand system consisting of a silsesquioxane‐derivatized thiol is also described.
Polymeric [(Me3Sn)3Rh(SCN)6]: A Novel “Super‐Prussian‐Blue” Derivative Containing the Nonlinear ‐SCN‐Sn‐NCS‐ Spacer
Authors: Siebel Eric , Fischer R. Dieter
Published: July 2007

The new coordination polymer [(Me3SnIV)3RhIII(SCN)6] = [Rh{μ‐(SCNSnMe3NCS)}3] (5) is readily accessible by straightforward self‐assembly of [Rh(SCN)6]3‐ and (dehydrated) {Me3Sn} ions. The architecture of 5 is strongly reminiscent of “super‐Prussian‐blue” systems reported earlier: there is a three‐dimensional (3‐D) framework involving {Rh8} pseudocubes as the basic building blocks, the Rh3+ ions being held apart by novel, nonlinear {SCN‐SnMe3‐NCS} spacers (d(Rh…︁Rh) = 1.27 nm). The complete lattice consists of two equivalent and independent, ideally interwoven 3‐D frameworks. Three homologues of 5 with slightly modified R3Sn units (R = Et, nPr and nBu) have been prepared as well, but display X‐ray powder diffraction patterns notably different from that of 5.
(CuI)2Cu3SbS3: Copper Iodide as Solid Solvent for Thiometalate ions
Authors: Pfitzner Arno
Published: July 2007

(CuI)2Cu3SbS3 was prepared by solid‐state reaction of stoichiometric amounts of CuI, Cu, S, and Sb. The crystal structure was determined from single crystals at room temperature and ‐ 80°C. Red‐orange (CuI)2Cu3SbS3 crystallizes in the orthorhombic system, space group Pnnm (no. 58) with a = 10.488(2), b = 12.619(2), c = 7.316(1) Å, V = 968.2(2) Å3 (20°C), and Z = 4. The distribution of the copper atoms was refined by using a Gram‐Charlier nonharmonic development of their atomic displacement parameters, which indicated an increasing dynamic disorder from ‐80°C to 20°C. Raman spectra of (CuI)2Cu3SbS3 are dominated by strong bands for [SbS3]3‐ units at 362 and 338 cm‐1. The compound melts at 492°C (DTA, onset). Conductivity measurements reveal high ionic conductivity (6.2 × 10‐5ω‐1 cm‐1 at 50°C, 2.9 × 10‐3 ω‐1 cm‐1 at 200°C) with an activation energy of 0.35 eV (40–275°C).
Local presentation of L1 and N‐cadherin in multicomponent, microscale patterns differentially direct neuron function in vitro
Authors: Shi Peng , Shen Keyue , Kam Lance C.
Published: July 2007

The ability to pattern multiple bioactive cues on a surface is valuable for understanding how neurons interact with their complex extracellular environment. In this report, we introduce a set of methods for creating such surfaces, with the goals of understanding how developing neurons integrate multiple biologically relevant signals and as a tool for studying interactions between multiple neurons. Multiple microcontact printing steps are combined on a single surface to produce an array of polylysine nodes, interconnected by lines of proteins based on the extracellular domains of L1 or N‐cadherin. Surprisingly, the N‐cadherin protein could also be directly printed onto surfaces while retaining its biological activity. Rat hippocampal neurons selectively attached to the polylysine nodes, differentially extending axonal and dendritic processes along the patterns of L1 and N‐cadherin, thus demonstrating control over neuron attachment and outgrowth. Combining these three biomolecules on a single surface revealed a highly complex pattern of protein recognition. Dendrites extended exclusively on N‐cadherin patterns, while axons exhibited a very high degree of selectivity on L1 patterns, preferentially at distances greater than 55 μm from the cell body. At shorter distances, axonal processes recognized both L1 and N‐cadherin, revealing a new aspect of neuron polarity and axon specification. This onset of L1 selectivity correlated with the establishment of intracellular L1 polarity, suggesting a functional outcome of the process of neuron polarization that has implications in development of neural tissues and creation of in vitro neuron networks. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007.
Summary of ‘Antibiotics for the prevention of acute and chronic suppurative otitis media in children’
Authors: Milne Andrea
Published: July 2007

This is a summary of a Cochrane review, published in this issue of EBCH, first published as: Leach AJ, Morris PS. Antibiotics for the prevention of acute and chronic suppurative otitis media in children. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD004401. DOI: 10.1002/14651858.CD004401.pub2.

Further information for this Cochrane review is available in this issue of EBCH in the accompanying Commentary and Characteristics and Key Findings Tables articles. Copyright © 2007 John Wiley & Sons, Ltd.
Summary of ‘Modification of the home environment for the reduction of injuries’
Authors: Milne Andrea
Published: July 2007

This is a summary of a Cochrane review, published in this issue of EBCH, first published as: Lyons RA, John A, Brophy S, Jones SJ, Johansen A, Kemp A, Lannon S, Patterson J, Rolfe B, Sander LV, Weightman A. Modification of the home environment for the reduction of injuries. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD003600. DOI: 10.1002/14651858.CD003600.pub2.

Further information for this Cochrane review is available in this issue of EBCH in the accompanying Commentary and Characteristics and Key Findings Tables articles. Copyright © 2007 John Wiley & Sons, Ltd.
Summary of ‘Written action plans for asthma in children’
Authors: Milne Andrea
Published: July 2007

This is a summary of a Cochrane review, published in this issue of EBCH, first published as: Bhogal S, Zemek R, Ducharme FM. Written action plans for asthma in children. Cochrane Database of Systematic Reviews 2006, Issue 3. Art. No.: CD005306. DOI: 10.1002/14651858.CD005306.pub2.

Further information for this Cochrane review is available in this issue of EBCH in the accompanying Commentary and Characteristics and Key Findings Tables articles. Copyright © 2007 John Wiley & Sons, Ltd.
Commentary on ‘Antibiotics for the prevention of acute and chronic suppurative otitis media in children’, with response from review author
Authors: van Benthem Peter Paul G.
Published: July 2007

This is a commentary on a Cochrane review, published in this issue of EBCH, first published as: Leach AJ, Morris PS. Antibiotics for the prevention of acute and chronic suppurative otitis media in children. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD004401. DOI: 10.1002/14651858.CD004401.pub2.

Further information for this Cochrane review is available in this issue of EBCH in the accompanying EBCH Summary and Characteristics and Key Findings Tables articles. Copyright © 2007 John Wiley & Sons, Ltd.
Commentary on ‘Nitric oxide for respiratory failure for infants born at or near term’
Authors: Cools Filip
Published: July 2007

This is a commentary on a Cochrane review, published in this issue of EBCH, first published as: Finer NN, Barrington KJ. Nitric oxide for respiratory failure in infants born at or near term. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD000399. DOI: 10.1002/14 651 858.CD000399.pub2.

Further information for this Cochrane review is available in this issue of EBCH in the accompanying EBCH Summary and Characteristics and Key Findings Tables articles. Copyright © 2007 John Wiley & Sons, Ltd.
Commentary on ‘Systemic antibiotics versus topical treatments for chronically discharging ears with underlying eardrum perforations’
Authors: Schilder Anne G. M. , Sanders Elisabeth A. M.
Published: July 2007

This is a commentary on a Cochrane review, published in this issue of EBCH, first published as: Macfadyen CA, Acuin JM, Gamble C. Systemic antibiotics versus topical treatments for chronically discharging ears with underlying eardrum perforations. Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.: CD005608. DOI: 10.1002/14 651 858.CD005608.

Further information for this Cochrane review is available in this issue of EBCH in the accompanying EBCH Summary and Characteristics and Key Findings Tables articles. Copyright © 2007 John Wiley & Sons, Ltd.
Characteristics and key findings for ‘Written action plans for asthma in children’
Authors: van Dalen Elvira , Offringa Martin , Kremer Leontien
Published: July 2007

These are the characteristics and key findings for a Cochrane review, published in this issue of EBCH, first published as: Bhogal S, Zemek R, Ducharme FM. Written action plans for asthma in children. Cochrane Database of Systematic Reviews 2006, Issue 3. Art. No.: CD005306. DOI: 10.1002/14 651 858.CD005306.pub2.

Further information for this Cochrane review is available in this issue of EBCH in the accompanying EBCH Summary and Commentary articles. Copyright © 2007 John Wiley & Sons, Ltd.
Characteristics and key findings for ‘Systemic antibiotics versus topical treatments for chronically discharging ears with underlying eardrum perforations’
Authors: van Dalen Elvira , Offringa Martin , Kremer Leontien
Published: July 2007

These are the characteristics and key findings for a Cochrane review, published in this issue of EBCH, first published as: Macfadyen CA, Acuin JM, Gamble C. Systemic antibiotics versus topical treatments for chronically discharging ears with underlying eardrum perforations. Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.: CD005608. DOI: 10.1002/14 651 858.CD005608.

Further information for this Cochrane review is available in this issue of EBCH in the accompanying EBCH Summary and Commentary articles. Copyright © 2007 John Wiley & Sons, Ltd.
Probabilistic evaluation of global seismic capacity of degrading structures
Authors: Koduru S. D. , Haukaas T. , Elwood K. J.
Published: July 2007

The present study addresses the probabilistic seismic capacity evaluation of the existing non‐ductile reinforced concrete structures that are vulnerable to shear, and thus axial, failures of their columns. The probability of structural collapse at a target lateral displacement imposed by seismic hazard is estimated by reliability analysis. For this purpose, the prevalent nonlinear static procedure is extended with finite element reliability analysis. The global structural model is enhanced by incorporating probabilistic capacity and post‐failure response models of individual columns. The challenges in the detection of collapse and the potential problems and remedies in the reliability analysis due to ‘gradient discontinuities’ are presented. In particular, ‘smoothing’ of the post‐failure response models is implemented to represent realistic member behaviour and to avoid non‐convergence in the reliability analysis. Finally, parameter importance measures are employed to identify the parameters with the highest contribution to the uncertainty in the structural performance. Copyright © 2007 John Wiley & Sons, Ltd.
A quantitative overview of glucose dynamics in the gliovascular unit
Authors: Barros L. F. , Bittner Carla X. , Loaiza Anitsi , Porras Omar H.
Published: July 2007

While glucose is constantly being “pulled” into the brain by hexokinase, its flux across the blood brain barrier (BBB) is allowed by facilitative carriers of the GLUT family. Starting from the microscopic properties of GLUT carriers, and within the constraints imposed by the available experimental data, chiefly NMR spectroscopy, we have generated a numerical model that reveals several hidden features of glucose transport and metabolism in the brain. The half‐saturation constant of glucose uptake into the brain (Kt) is close to 8 mM. GLUT carriers at the BBB are symmetric, show accelerated‐exchange, and a Km of zero‐trans flux (Kzt) close to 5 mM, determining a ratio of 3.6 between maximum transport rate and net glucose flux (Tmax/CMRglc). In spite of the low transporter occupancy, the model shows that for a stimulated hexokinase to pull more glucose into the brain, the number or activity of GLUT carriers must also increase, particularly at the BBB. The endothelium is therefore predicted to be a key modulated element for the fast control of energy metabolism. In addition, the simulations help to explain why mild hypoglycemia may be asymptomatic and reveal that [glucose]brain (as measured by NMR) should be much more sensitive than glucose flux (as measured by PET) as an indicator of GLUT1 deficiency. In summary, available data from various sources has been integrated in a predictive model based on the microscopic properties of GLUT carriers. © 2007 Wiley‐Liss, Inc.
Kleine Ringe, 86. Versuche zur Darstellung von Alkyltri‐tert‐butyltetrahedranen auf dem Cyclopentadienon‐Weg; photochemisches Verhalten der Cyclopentadienone
Authors: Maier G. , Franz L. H. , Boese Roland
Published: July 2007

Small Rings, 86. – Attempts to Synthesize Alkyltri‐tert‐butyltetrahedranes by the Cyclopentadienone Route; Photochemical Behavior of the Cyclopentadienones

Only the Tetra‐tert‐butyltetrahedranes 8a–c can be synthesized by photochemical CO extrusion from the corresponding cyclopentadienones 6a–c. This strategy fails with other cyclopentadienones like 6d–f.
Kleine Ringe, 87. Suche nach alternativen Wegen zum Tetra‐tert‐butyltetrahedran; Synthese sterisch überladener Verbindungen
Authors: Maier Günther , Rang Harald , Emrich Rolf
Published: July 2007

Small Rings, 87. – Search for Alternative Routes to Tetra‐tert‐butyltetrahedrane; Synthesis of Sterically Overcrowded Molecules

Ketene 3 can be isomerized to triclopentanone 2 by treatment with silica gel. Thus, the yield of tetrahedrane 5, which is formed upon irradiation of 2, has been improved. On the other hand, diazoketone 10 cannot be used as a precursor for 2. This failure is due to steric hindrance. For the same reason cyclobutadiene 4 is a very poor candidate for Diels‐Alder cycloadditions.
Kleine Ringe, 88. Reaktionen von Tetra‐tert‐butyltetrahedran: Oxidation zum Radikal‐Kation als einleitender Schritt
Authors: Maier Günther , Rang Herald , Emrich Rolf , Gries Stefan , Irngartinger Hermann
Published: July 2007

Small Rings, 88. – Reactions of Tetra‐tert‐butyltetrahedrane: Oxidation to the Radical Cation as the First Step

The chemistry of tetrahedrane 1 and cyclobutadiene 3 is governed by the initial formation of radical cation 2. In spite of the high steric hindrance 2 cannot be isolated as a radical‐ion pair. Reaction of 3 with O2 generates the oxete 21 which is surprisingly stable (up to 200°C).
Kleine Ringe, 90. Peralkyl‐substituierte Tetrahedrane
Authors: Maier Günther , Fleischer Frank , Kalinowski Hans‐Otto
Published: July 2007

Small Rings, 90. – Peralkyl‐Substituted Tetrahedranes

Photolysis of the diazo compounds 4a, b generates adaman‐tyltri‐tert‐butyltetrahedrane (9a) and tri‐tert‐butylisopropyltetrahedrane (9b), and the corresponding cyclobutadienes 10a, b. In contrast to tetrahedrane 9a, which results from an intramolecular addition in carbene 7a and also from photoisomerization of cyclobutadiene 10a, the only source for tetrahedrane 9b is the cheletropic cycloaddition of the carbenic center to the cyclopropene double bond in the photochemically produced carbene 7b. Tetrahedrane 9b is remarkable in its kinetic and thermal instability, which is caused by the reduced „corset effect”︁ in this compound. An additional access to this tetrahedrane is possible via the diazomethanes 34A and 34B. The pyridazines 17b and 41, which are formed by thermolysis of the diazo compounds 4b, 34A and 34B lead to the azetes 19 and 43. Last but not least 17b and 41 are interesting molecules themselves because of their inherent chirality.
Terpenes and terpene derivatives, XXXIII. Synthesis of rac‐cis‐ and ‐trans‐dracunculifoliol and their 10‐epimers
Authors: Weyerstahl Peter , Marschall Helga , Schneider Kathleen
Published: July 2007

The cis‐aldehyde 9, a key intermediate in the total synthesis of cis‐dracunculifoliol (1) previously isolated from Vassoura oil, was prepared starting from the bicyclic enone 5 via the nitrile 8. Grignard reaction of 9 led exclusively to epi‐1. Oxidation to the ketone 10 followed by reduction gave a separable mixture of the natural isomer 1 and epi‐1. – The synthesis of trans‐dracunculifoliol (2) starts with the 6‐methoxytetralone 14. After some usual steps, the trans‐octalin 17 was obtained. MMPP‐HIO4 oxidation gave compound 19 which was transformed into the iodo ester 26, precursor of the hydrindane ester 27. Analogously to the synthesis of epi‐1 the epi‐trans‐dracunculifoliol (epi‐2) was formed via alcohol 28 and aldehyde 29. Oxidation ( 30) and reduction furnished the natural trans alcohol 2. – Olfactory evaluation of the purified isomers 1, epi‐1, 2, and epi‐2 showed that all of them possess only a weak, woody odor. Therefore, the dracunculifoliols 1 and 2 are not responsible for the typical earthy, leathery, and spicy odor of the Vassoura oil.
Steroidal cyclobutanones, V. the baeyer‐villiger rearrangement of α‐substituted β‐spirocyclobutanones
Authors: Paryzek Zdzislaw , Blaszczyk Krzysztof
Published: July 2007

The reaction of the steroidal spiro‐α,α‐dichlorocyclobutanone 1 carried out in basic H2O2/MeOH/THF solution proceeds with cine substitution leading to the intermediate α‐chloro‐α‐methoxycyclobutanone 7 followed by the Baeyer‐Villiger rearrangement giving the spiro‐α‐chloro‐γ‐methoxylactone 9 as a mixture of four stereoisomers. The oxidation of the α‐chlorocyclobutanone 12 gives the methoxylactone 10 resulting also from a cine substitution preceding the rearrangement. The unusual transformation of 1 to the succinic anhydride derivative 14 is also observed.
Regioselectivities in the catalyzed conjugate addition of organoaluminium and organotitanium reagents to sterically hindered enones: Investigation of the methylation of 10β‐methyl‐Δ1,9‐2‐octalones
Authors: Kabbara Jazid , Flemming Steffen , Nickisch Klaus , Neh Harribert , Westermann Jürgen
Published: July 2007

Regioselectivities in Michael‐type reactions of organoaluminium and organotitanium reagents with sterically hindered carbonyl compounds 1 and 5 concerning 1,2‐ versus 1,4‐addition were determined. Throughout this investigation Me3Al/cat. Ni(acac)2 was found to be the most useful reagent for strongly hindered systems.
Planar chiral systems, IV. An efficient route for the preparation of 5‐formyl‐4‐hydroxy[2.2]paracyclophane (FHPC)
Authors: Hopf Henning , Barrett David G.
Published: July 2007

For the preparation of the title compound, 4‐hydroxy[2.2]paracyclophane (1) is first converted to the carbamate 2. Metalation of 2 with sec‐butyllithium yields an ortho‐anion which after trapping with dimethylformamide and acidic work‐up provides 6 in 64% yield. Further application of the cyclophane anion include its capture by trimethylsilyl chloride to the trimethylsilyl derivative 3 (76%) and its Fries rearrangement to the phenol 4 (78%). The spectroscopic and analytical data of the new compounds are described in full detail.
Studien zur Chemie von thienoanellierten O,N‐ und S,N‐haltigen Heterocyclen, 8. Synthese eines racemischen, thienoanalogen Diltiazems mit potentieller Calciumkanal blockierender Wirkung
Authors: Laimer Ingrid , Erker Thomas
Published: July 2007

Studies on the Chemistry of Thieno‐Annulated O,N‐ and S,N‐Containing Heterocycles, 8[1].–Synthesis of a Racemic, Thieno Analogue Diltiazem with Potential Ca2+Antagonistic Activity

The synthesis of the thieno analogue diltiazem cis‐8‐[2‐(di‐methylamino)ethyl]‐5,6,7,8‐tetrahydro‐5‐(4‐methoxyphenyl)‐7‐oxothieno[3,2‐b][1,4]thiazepin‐6‐yl acetate (1) is described. Reaction of 3‐bromo‐2‐nitrothiophene with Na2S · 9H2O yields the intermediate 3‐mercapto‐2‐nitrothiophene (6), which reacts with the racemic glycidate 7 to give the racemic threo compound 10. Reduction and cyclization of 10 furnish the thieno [3,2‐b][1,4]thiazepine derivative 12. N‐Alkylation and acetylation of the hydroxy group of 12 leads to 1.
Triazolines, 35. 2‐aminoaziridines: Unstable intermediates in thermal decomposition of 5‐amino‐v‐triazolines
Authors: Pocar Donato , Roversi Elena , Trimarco Pasqualina , Valgattarri Guido
Published: July 2007

Pyrolysis of 4‐aryl‐5‐amino‐v‐triazolines 4 affords two products: benzanilides 5 and acetamidines 6. Pyrolysis of 4 with DMAD under argon produces 1‐aza‐1,3‐dienes 8 and 2‐pyrrolines 9. The reaction mechanism of this transformation is discussed. 2‐Aminoaziridines are shown to be key intermediates in this reaction.
Cyclophanes, XXXIX. The Structure of the Dicyanoacetylene Adducts of [2.2]Paracyclophane
Authors: Hopf Henning , Witulski Bernhard , Jones Peter G. , Schomburg Dietmar
Published: July 2007

The structures of the 1:1 and 1:2 addition products of dicyanoacetylene (2) to [2.2]paracyclophane (1) have been determined by X‐ray structural analysis as 3 and 5, respectively. In contrast to literature reports, the latter possesses the „crossed”︁ double barrelene configuration. On irradiation 3 isomerizes to the semibullvalenophane 4 as was also shown by X‐ray structural analysis.
Rearrangement and cycloreversion of Diels‐Alder adducts of cyclic 1,3‐dienes to norbornadienes. A novel homo‐cope rearrangement. Evidence for competitive pericyclic and diradical processes
Authors: Hochstrate Dirk , Klärner Frank‐Gerrit
Published: July 2007

On thermolysis of endo,endo‐5, endo,endo‐17, and endo,exo‐17 (the endo,endo and endo,exo Diels‐Alder adducts of cyclopentadiene 7 or dimethylfulvene 15 to norbornadiene 8 or 7‐isopropylidenenorbornadiene 20), a novel type of homo‐Cope rearrangement leading to 6, 21, and 23a, respectively, competes with the retro‐Diels‐Alder reactions. According to a force‐field analysis of the kinetic parameters, the competitive reactions (rearrangement and retro‐Diels‐Alder reaction) of endo,endo‐5 occur in a pericyclic fashion whereas in the isopropylidene‐substituted systems stepwise processes compete with the corresponding pericyclic reactions. Indirect experimental evidence for this assumption comes from a stereochemical analysis of the refro‐Diels‐Alder reaction in the cis‐5,6‐dideuterionorbornene derivatives exo‐36‐d2, endo‐36‐d2 and exo‐39‐d2, endo‐39‐d2 occurring stereospecifically in the case of exo‐36‐d2, endo‐36‐d2 and non‐stereospecifically in the case of exo‐39‐d2, endo‐39‐d2. The change in mechanism is rationalized by a different (allyl vs. pentadienyl) stabilization of the potential diradical intermediates in the stepwise reactions.
Cinnolines and pyrazolopyridazines. — Novel synthetic and mechanistic aspects of the Richter reaction
Authors: Vasilevsky Sergei F. , Tretyakov Eugene V.
Published: July 2007

The thermal cyclization of 2‐alkynylbenzenediazonium salts 2 known as the Richter reaction and leading, as described in the literature, only to 4‐hydroxycinnolines 6 has been studied. A new probable route to these compounds involving intermediate formation of the 4‐chlorocinnolines 4 followed by hydrolysis of the latter to 6 is discussed. A new understanding of the reaction mechanism has induced us to change the reaction conditions in order to synthesize some 4‐bromo‐ (5), 4‐chloro‐ (4), and 4‐hydroxycinnolines 6 as well as 4‐bromo‐(8b) and 4‐chloropyrazolopyridazine 8a.
Reactions of 1,3,5‐Tri‐tert‐butylcyclopentadiene formation of a tetracyclo[5.2.1.02,6.03,10]deca‐4,8‐diene
Authors: Dehmlow Eckehard V. , Bollmann Christof
Published: July 2007

Title compound 1 is sterically shielded to such an extent that many „normal”︁ reactions cannot occur. It is possible, however, to prepare the carboxylic acid 2, its acyl chloride 3 and the oxidation product 4. Furthermore, halogen substitutions to yield 5 and 6 and trialkylstannations to give 8a, b can be performed. Oxidative dimerization of 1 leads to 7, and this can be rearranged to the totally unexpected tetracyclic compound 9.
Antibiotics from gliding bacteria, LXIV. Isolation and structure elucidation of sorangiolides A and B, novel macrocyclic lactone carboxylic acids from Sorangium cellulosum
Authors: Jansen Rolf , Irschik Herbert , Meyer Holger , Reichenbach Hans , Wray Victor , Schomburg Dietmar , Höfle Gerhard
Published: July 2007

Two novel metabolites, sorangiolide A (1) and B (2), were isolated from the mother liquors and side fractions of the sorangicin A pilot‐scale production. Their structures were elucidated by 2D‐NMR spectroscopy and mass spectrometry as 18‐membered macrolactones with a C11‐carboxylic acid side chain. Sorangiolide B (2) differs from A (1) by an additional hydroxyl group at C‐6 in the side chain. The absolute configuration of sorangiolide A (1) was established by X‐ray structure analysis. The sorangiolides show a weak antibiotic activity against Gram‐positive bacteria.
Enzymes in organic synthesis, 23. Chemo‐enzymatic synthesis of (5R,6S)‐6‐acetoxyhexadecan‐5‐olide — the major component of the mosquito oviposition attractant pheromone
Authors: Henkel Birgitta , Kunath Annamarie , Schick Hans
Published: July 2007

The methyl ester rac‐4a of (5R*,6S*)‐5,6‐dihydroxyhexadecanoic acid was prepared by a Wittig reaction of (4‐carboxybutyl)triphenylphosphonium bromide (2) with undecanal (1) followed by esterification with methanol and cis dihydroxylation with osmium (VIII) oxide/N‐methylmorpholine N‐oxide. After conversion of the dihydroxy ester rac‐4a into (5R*,6S*)‐6‐hydroxyhexadecan‐5‐olide (rac‐5) by lactonization (5R,6S)‐6‐acetoxyhexadecan‐5‐olide (6), the mosquito oviposition attractant pheromone, was obtained by an enantioselective lipase‐catalyzed acetylation with vinyl acetate. In an alternative route the dihydroxy ester rac‐4a was subjected to a lipase‐catalyzed lactonization, which afforded as the main product (5S,6R)‐6‐hydroxyhexadecan‐5‐olide (ent‐5), the enantiomer of the deacetylated pheromone.
Studies on electron transfer as mechanistic concept for [4 + 2] cycloadditions, 1. Cycloadditions of 1,4‐bis(dimethylamino)‐1,3‐butadiene to electron‐deficient olefins
Authors: Lücking Karin , Rese Michael , Sustmann Reiner
Published: July 2007

(E,E)‐1 and (E,Z)‐1,4‐bis(dimethylamino)‐1,3‐butadiene (2) as model systems for highly electron‐rich dienes were allowed to react with olefins of increasing electron‐acceptor capacity under standard concentrations (0.4 M solutions of diene and dienophile) and at reaction temperatures from −50°C to a maximum of +60°C (slow decomposition of the diene). Methyl acrylate (3), acrylonitrile (4), and dimethyl methylfumarate (6) did not form cycloadducts with 1 at 35°C in six weeks. Isopropylidenemalononitrile (5) undergoes dimerization. Maleo‐ (9) and fumaronitrile (10) add to 1 with retention of stereochemistry ( ≥98%). Dimethyl maleate (7) isomerizes under the reaction conditions to dimethyl fumarate (8) and reacts with 1 to the cycloadduct of 8. N‐Methylmaleimide (11) gave the expected cycloadduct. The monosubstituted C atoms of the CC double bond of 1,1,2‐tris(methoxycarbonyl)ethene (12) and 2‐cyano‐1,1‐bis(methoxycarbonyl)‐ethene (13) add to C‐2 of 1 to form zwitterions which stabilize themselves by a 1,3‐hydrogen shift to 24 and 25. The reactions of 1 with 1,1‐dicyano‐2‐methoxycarbonylethene (14), 1,1‐dicyano‐2,2‐bis(methoxycarbonyl)ethene (15), and tetracyanoethene (18) provided, though very reactive, no isolable cycloadducts or other identifiable products. Dimethyl dicyanomaleate (16) and dimethyl dicyanofumarate (17) lead in non‐stereospecific reactions with 1 to the same cycloadduct even at −50°C in dichloromethane. The same cycloadduct is obtained from 2 and 17. For the reactions of 16 and 17 with 1 electron transfer from diene to dienophile could be demonstrated. Intermediates were detected 1H‐NMR‐spectroscopically at −95°C which transformed into the cycloadduct when warmed to−50°C. A comparison of the preparative results with oxidation potentials of 1 and 2, and the reduction potentials of the olefins shows, that electron transfer is possible when oxidation and reduction potential are close together. It is concluded from the loss of stereochemistry during the cycloadduct formation in those cases (16 and 17) where electron transfer is observed, and furthermore from retention of stereochemistry (9 and 10) when no electron transfer could be detected, that electron transfer may be a possibility in [4 + 2] cycloadditions, but that it is not the general mechanism of the Diels‐Alder reaction.
Optimised preparation of 1,5‐dialkylsemibullvalenes
Authors: Quast Helmut , Dietz Thomas , Peters Eva‐Maria , Peters Karl , von Schnering Hans Georg
Published: July 2007

Askani's synthesis of the 1,5‐dialkylsemibullvalenes 1a and c was optimised on a gram scale. The as yet unknown trimethylenesemibullvalene 1b was obtained according to the same protocol which also greatly improved a recent synthesis of barbaralane (2). Allylic brominations of the dienes 5 + 6 with N‐bromosuccinimide yielded complex mixtures of 7–10. Depending on the substitution pattern at the apical carbon atoms C‐1 and C‐5 of the bicyclo[3.3.0]octadiene system, the intermediate allylic radicals are attacked preferentially either from the exo (R = Me) or from the endo face [R, R = (CH2)3, (CH2)4]. Reductive cyclisations of the dibromides 9 and exo,exo‐15 were carried out with a sonicated suspension of an activated zinc‐copper couple in tetraglyme. Sweeping of the volatile products from the reaction mixtures with nitrogen at elevated temperatures allowed the convenient isolation of the semibullvalenes 1 and barbaralane (2) in reasonable purities (92–97%) and yields (57–82%).
Synthesis of perylene‐3,4‐dicarboximides — Novel highly photostable fluorescent dyes
Authors: Feiler Leonhard , Langhals Heinz , Polborn Kurt
Published: July 2007

Perylene‐3,4‐dicarboximides 2 are obtained by a decarboxylizing condensation of moderately sterically hindered primary amines with perylene‐3,4,9,10‐tetracarboxylic 3,4:9,10‐bisanhydride (3) in the presence of water. Perylene‐3,4‐dicarboxylic anhydride (4) is prepared by hydrolysis of the imides with KOH in tert‐butyl alcohol. The anhydride may be condensed with any primary amine to the corresponding imide. The imides are highly fluorescent and very photostable dyes.
Syntheses and conformations of persubstituted inverse calixarenes
Authors: Schätz Rolf , Weber Christian , Schilling Gerhard , Oeser Thomas , Huber‐Patz Ursula , Irngartinger Hermann , von der Lieth Claus‐W. , Pipkorn Rüdiger
Published: July 2007

A series of ten inverse calix[n]arenes (2–11) bearing four to thirteen benzene units were prepared by starting from 3,4,5‐trimethoxybenzaldehyde followed by LC separation on silica gel. In 2–11 the substitution pattern is interchanged compared with the usual calixarenes. The conformational analysis was undertaken by variable temperature 1H‐NMR spectroscopy and by MM2 calculations. Calix[4]arene 2 is a rigid molecule and shows the 1,3‐alternate conformation which in addition was proven by X‐ray analysis. At low temperatures the calix[5]arene 3 adopts the uudod conformation, where a methyl group of one benzene unit residues in the cavity of the macrocycle. At low temperature calix[6]arene 4 forms an 1:2 equilibrium between the 1,3,5‐alternate (ududud; 4E) and the uududu (4B) conformation. Conformation 4B can be regarded as an intramolecular combination of a cone and an alternate arrangement of the benzene units. The calix[8]‐arene shows the highest ΔG* value of the series and adopts an uuududdd conformation at low temperature. The inverse calixarenes 5 and 7–11 bearing seven and nine to thirteen aromatic units, respectively, are conformationally highly flexible systems even at low temperatures.
Stereoselective synthesis of oligo(tetrahydrofurans): Linear and convergent routes to bi‐ and tertetrahydrofurans
Authors: Koert Ulrich , Stein Matthias , Wagner Holger
Published: July 2007

The „dimeric”︁ and „trimeric”︁ oligo(tetrahydrofurans) (oligo‐THFs) 24, 28, 32, and 38 were synthesized stereoselectively according to a linear and a convergent synthetic strategy. The oligo‐THFs thus obtained are important intermediates for the synthesis of artificial ion channels. Furthermore, they can be used in the total synthesis of Annonaceae acetogenins, a class of natural occurring oligo‐THFs with promising pharmacological properties.