Synthesis and purity assessment of tetra- and pentaacyl lipid A of Chlamydia containing (R)-3-hydroxyicosanoic acid

Based on structural data of lipid A from Chlamydia trachomatis strains, chemically pure tetra- and pentaacyl 1,4′-bisphosphoryl as well as the related 4′-monophosphoryl derivatives of lipid A were synthesized. (R)-3-Hydroxyicosanoic acid as a chiral constituent was prepared via Noyori-reduction of methyl-3-oxoicosanoic acid. Synthetic intermediates were O-acylated with myristoic acid residues at positions 3 and 3′ and N-acylated with (R)-3-hydroxyicosanoic acid at both glucosamine units. Efficient purification methods for highly hydrophobic long-chain tri-, tetra- and pentaacyl progenitors of lipid A have been developed. Purity and homogeneity of the synthetic target compounds were confirmed by NMR and MS-data as well as a sensitive immunostaining approach. The tetra- and pentaacyl species serve as biomedical probes to investigate the endotoxic potential of chlamydial lipid A and to clarify its role in Chlamydia associated infections.     

Annelated tricyclic thiophenes and their photophysical properties

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Dinuclear copper(ii) complex with novel N,N’,N”,O-tetradentate Schiff base ligand containing trifluoromethylpyrazole and hydrazone moieties

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Growth in a restricted solid on solid model with correlated noise

We introduce correlated growth into a restricted solid on solid model (RSOS), a stochastic deposition model with a constraint on neighboring height differences. A two-dimensional lattice model is used in which particles are deposited via horizontal Levy flight steps with a step length distribution exponentf. Though RSOS is in the same universality class as ballistic deposition for uncorrelated deposition, it appears to depart from it for strong correlations. Forf=1, the short-range limit is reached and both exponents and, which describe the dependence of surface width on time and strip length, tend to 1. Forf>1 we retreat to an enhanced algorithm, searching for growth sites which become excessively rare. We find an unusual short-time dependence, but still tends to 1. The number of growth sitesG shows saturation forf<1, while forf1 we observeG/L0 as the strip lengthL increases. Finally, we test directly the relationship of noise-noise correlation strength tof, and find that a direct comparison between correlated growth models and theoretical predictions for growth with correlated noise is so far unjustified.     

Structure and swelling-release behaviour of poly(vinyl pyrrolidone) (PVP) and acrylic acid (AAc) copolymer hydrogels prepared by gamma irradiation

Copolymer network hydrogels were prepared by gamma irradiation of aqueous solutions of poly(vinyl pyrrolidone) (PVP) and acrylic acid monomer (AAc). The composition of the final hydrogels compared to the composition of the initial preparation solutions of hydrogels was determined. The chemical structure and nature of bonding was characterized by IR spectroscopy analysis, while the thermal durability of the prepared hydrogels was assessed by thermogravimetric analysis (TGA). The kinetic swelling in water and the pH-sensitivity of PVP/AAc copolymer hydrogels was studied. The drug release properties of PVP/AAc hydrogels taking methyl orange indicator as a drug model was investigated. The IR spectra indicate the formation of copolymer networks, whereas the TGA study showed that the PVP/AAc hydrogels possess higher thermal stability than pure PAAc and lower than PVP hydrogels. The kinetic swelling in water showed that all the hydrogels reached equilibrium after 24 h and that the degree of swelling increases with increasing the ratio of AAc in the initial feeding solutions. It was found that the degree of swelling of PVP/AAc hydrogels increases greatly within the pH range 4-7 depending on composition.     

Resolution limits in magic-angle rotation NMR spectra of polycrystalline solids

Dependence of linewidth in porton-decoupled ¹³C NMR spectra of diamagnetic polycrystalline samples on external magnetic field strength is studied. Spectral resolution is limited by magnetic heterogencity of powder samples. It is suggested that in magic-angle rotation spectra, the linewidth is determined by the amsotropy of the magnetic susceptibility Δ_xυ rather than _xυ of the crystallites.     

A novel methodology for the synthesis of complexes containing long carbon chains linking metal centres: molecular structures of [Ru(dppe)Cp*]2(mu-C14) and [Co3(mu-dppm)(CO)7]2(mu3:mu3-C16)

Elimination of AuX(PR3)(X = halogen, R = Ph, tol) occurs readily in reactions between compounds containing C(sp)- or C(sp2)-X bonds and alkynyl or polyynyl gold(I) complexes; this reaction has been applied to the syntheses of complexes containing a variety of metal centres linked by C(n) chains (n up to 16).     

Vibrational spectra and conformational isomerism of calixarene building blocks: 2-benzylphenol

The conformations and vibrational spectra of 2-benzylphenol have been analysed within the framework of scaled quantum mechanics. It is shown that the solid-state conformation of the 2-benzylphenol molecule corresponds to one of four potential energy minima predicted by non-empirical quantum chemical calculations for the isolated molecule. In the molten state and in diluted CCl4 solutions of the title compound this conformer coexists with another two spectroscopically detected conformations. The presence of several conformers gives rise to the observation of the corresponding number of vsCH2 and vasCH2 bands in the IR spectra, thus providing experimental evidence of the conformational sensitivity of the vCH2 frequencies. It is shown that vCH2 wavenumbers of different kinds of molecules, containing diphenylmethane fragments, are determined by the dihedral angles between the planes of the aromatic rings and the plane of the connecting methylene bridges, except for the case of short intramolecular contacts with the participation of the methylene protons.     

Chemical synthesis of the innate immune modulator – bacterial d-glycero-β-d-manno-heptose-1,7-bisphosphate (HBP)

The bacterial metabolite and potent innate immune modulator d-glycero-β-d-manno-heptose-1,7-bisphosphate (HBP) and its α-configured counterpart d-glycero-α-d-manno-heptose-1,7-bisphosphate were synthesized via stereoselective anomeric phosphorylation of the peracetylated d,d-heptose 7-dibenzylphosphate by exploiting different nucleophilicity of equatorial and axial lactols in the d-manno-series. We also report a novel approach for anomeric phosphorylation using modified Mitsunobu reaction conditions and provide the first full structural characterization of HBP. The first chemical synthesis of HBP offers access to an anomerically pure structurally defined probe for biological studies and to a lead compound operating as a powerful stimulator of intracellular signaling for possible therapeutic immunomodulation.