A Diastereoselective Preparation of 7-Ethyl-7-methylbicyclo[3.2.0]HEPT-2-en-6-one(1)

Alkylation of 7-endo-ethylbicyclo[3.2.0]hept-2-en-6-one (2a) and 7-endo-methylbicyclo[3.2.0]hept-2-en-6-one (2b) with lithium diisopropylamide (LDA) and the appropriate alkyl iodide (methyl and ethyl iodide, respectively) afforded the title compound such that alkylation had occurred exclusively on the exo face of the bicyclo[3.2.0] system.     

A. Critical Evaluation of the Knorr Synthesis of Tpifluoromethylpyrroles and the Reactivity of Diethyl 4-Trifluoromethyl-2-Methylpyrrole-3, 5-Dicarboxylate.

β-Trifluoromethyl pyrroles are readily obtained by the Knorr synthesis, but the procedure fails for the preparation of the the α-isomers. The β-trifluoromethyl group reacts with alkoxide anions and is reduced with lithium aluminium hydride.     

Development and optimization of an integrated PDMS based‐microdialysis microchip electrophoresis device with on‐chip derivatization for continuous monitoring of primary amines

An all‐PDMS on‐line microdialysis‐microchip electrophoresis with on‐chip derivatization and electrophoretic separation for near real‐time monitoring of primary amine‐containing analytes is described. Each part of the chip was optimized separately, and the effect of each of the components on temporal resolution, lag time, and separation efficiency of the device was determined. Aspartate and glutamate were employed as test analytes. Derivatization was accomplished with naphthalene‐2,3,‐dicarboxyaldehyde/cyanide (NDA/CN^?), and the separation was performed using a 15‐cm serpentine channel. The analytes were detected using LIF detection.     

Investigation of the inclusion of the herbicide cycluron in native cyclodextrins by X-ray diffraction,nuclear magnetic resonance spectroscopy and isothermal titration calorimetry

The formation of inclusion complexes between the native cyclodextrins (CDs) and the urea herbicide cycluron has been investigated both in solution and in the solid state. Single-crystal X-ray structures of both the uncomplexed guest and the β-CD·cycluron complex were determined while powder X-ray diffraction was used to confirm complexation between γ-CD and cycluron in the solid state. Solution-state complexation between the herbicide and α-, β- and γ-CD was established using ¹H NMR spectroscopy and isothermal titration calorimetry (ITC). From the ¹H NMR spectroscopic studies 1:1 complex stoichiometry was indicated in all cases and association constant values (K) were determined as 228, 3254 and 155 for the complexes α-CD·cycluron, β-CD·cycluron and γ-CD·cycluron, respectively. Assigning a 1:1 host–guest ratio, the ITC technique produced K values of the same order as those determined using the spectroscopic method. The thermodynamic parameters ΔH, ΔS and ΔG obtained using ITC provide insights into the driving forces involved during complex formation.     

Molecular complexity and the control of self-organising processes

In this article we investigate the complexity of the molecular architectures of liquid crystals based on rod-like mesogens. Starting from simple monomeric systems founded on fluoroterphenyls, we first examine the effects of aromatic core structure on mesophase formation from the viewpoint of allowable polar interactions, and then we model these interactions as a function of terminal aliphatic chain length. By incorporating a functional group at the end of one, or both, of the aliphatic chains we study the effects caused by intermolecular interfacial interactions in lamellar phases, and in particular the formation of synclinic or anticlinic modifications. We then develop these ideas with respect to dimers, trimers, tetramers, etc. We show, for dendritic systems, that at a certain level of molecular complexity the local mesogenic interactions become irrelevant, and it is gross molecular shape that determines mesophase stability. The outcome of these studies is to link the complexity of the molecular interactions at the nanoscale level, which lead to the creation of the various liquid-crystalline polymorphs, with the formation of mesophases that are dependent on complex shape dependencies for mesoscopic supermolecular architectures.     

Synthesis and molecular structure of 4,4,5,5-tetramethyl-2-(1-(phenylsulfonyl)propan-2-yl)-1,3,2-dioxaborolane

The compound 4,4,5,5-tetramethyl-2-(1-(phenylsulfonyl)propan-2-yl)-1,3,2-dioxabo- rolane has been prepared by the rhodium catalyzed hydroboration of allyl phenyl sulfone and characterized by a single crystal X-ray diffraction study. The title compound crystallized in the monoclinic space group P2₁/c, with cell parameters a=16.0728(8) ?, b=9.8884(5) ?, and c=10.1926(5) ?, β=92.067(1)°, Z=4, and V=1618.90(14) ?³. The structure was solved by direct methods and refined to a final R=0.0449 for 3627 reflections with I>2σ(I). No significant intramolecular or intermolecular interaction is observed with the Lewis acidic boron atom.     

Achieving High Affinity towards a Bacterial Lectin through Multivalent Topological Isomers of Calix[4]arene Glycoconjugates

A family of seven topologically isomeric calix[4]arene glycoconjugates was prepared through the synthesis of a series of alkyne‐derivatised calix[4]arene precursors that are suitable for the attachment of sugar moieties by microwave‐assisted copper(I)‐catalysed azide–alkyne cycloaddition (CuAAC). The glycoconjugates thus synthesised comprised one mono‐functionalised derivative, two 1,2‐ or 1,3‐divalent regioisomers, one trivalent and three tetravalent topoisomers in the cone, partial cone or 1,3‐alternate conformations. The designed glycoconjugates were evaluated as ligands for the galactose‐binding lectin PA‐IL from the opportunistic bacterium Pseudomonas aeruginosa, a major causative agent of lung infections in cystic fibrosis patients. Binding affinities were determined by isothermal titration calorimetry (ITC), and the interaction with the lectin was shown to be strongly dependant on both the valence and the topology. Whereas the trivalent conjugate displayed enhanced affinity when compared to a monosaccharide model, the tetravalent conjugates are to‐date the highest‐affinity ligands measured by ITC. The topologies presenting carbohydrates on both faces of calixarene are the most potent ones with dissociation constants of approximately 200 nM . Molecular modelling suggests that such a multivalent molecule can efficiently chelate two of the binding sites of the tetrameric lectin; this explains the 800‐fold increase of affinity achieved by the tetravalent molecule. Surface plasmon resonance (SPR) experiments confirmed that this glycoconjugate is the strongest inhibitor for binding of PA‐IL to galactosylated surfaces for potential applications as an anti‐adhesive agent.     

Europium substitution into intermetallic phases grown in Ca/Zn flux

Replacement of calcium with europium in the phases Ca₂₁Ni₂Zn₃₆ and CaNi₂Zn₃ was attempted to explore the possibility of substitution in metal flux reactions and potential magnetic interactions between closely spaced Eu²⁺ ions. Limited substitution occurs when Eu is added to the reaction of nickel in a Ca/Zn flux mixture, up to stoichiometries of Eu_5.8(3)Ca_15.2(3)Ni₂Zn₃₆ and Eu_0.42(8)Ca_0.58(8)Ni₂Zn₃. Structural characterization and magnetic susceptibility studies on Eu_xCa_21−xNi₂Zn₃₆ phases indicate that the Eu and Ca ions do not form an even solid solution on their sites, but instead segregate in separate regions of the crystals. The europium-rich regions of the samples order ferromagnetically, with T_C dependent on the size of the clusters. If the concentration of Eu in the flux is raised above 20 mol%, a new compound Eu_1.63(1)Ca_1.37(1)Ni₂Zn₃ (Cmcm, a=4.1150(5) Å, b=16.948(2) Å, c=10.302(1) Å, Z=4, R₁=0.0396) is produced.