Heterocyclic variants of 1,5-Benzodiazepine system. VII. Synthesis of substituted 2a-Phenyl-4-methylsulfonyl-2-methoxy-1,2,2a,3-tetrahydroazeto[1,2-a][1,5]benzodiazepin-1-ones

The preparation of novel 2a-phenyl-4-methylsulfonyl-2-methoxy-1,2,2a,3-tetrahydroazeto[1,2-a][1,5]-benzodiazepin-1-ones is described. The structure of all the products was corroborated by ir, mass spectrometry and ¹H and ¹³C-nmr.     

Synthesis, characterisation and magnetic properties of octahedral chromium(III) compounds with six C-donor ligands

The homoleptic, square pyramidal organochromium(III) compound [NBu(4)](2)[Cr(C(6)F(5))(5)] (1) reacts with excess organic isocyanides, CNR [R = (t)Bu, 2,6-dimethylphenyl (Xy)], under dissociation of the apical C(6)F(5) ligand to give the more saturated, singly charged complexes [NBu(4)][trans-Cr(C(6)F(5))(4)(CNR)(2)] [R = (t)Bu (2), Xy (3)], containing six monodentate C-donor ligands. These compounds exhibit an axially distorted octahedral structure (single-crystal X-ray diffraction) with the four C(6)F(5) groups defining the equatorial positions and the CNR ligands occupying the axial ones. Compounds 2 and 3 both behave as spin quartet species (S = 3/2) at microscopic level (EPR spectroscopy), their macroscopic magnetic properties depending upon the nature of the terminal R group, as established by magnetisation measurements. When the R substituent is the saturated alkyl group (t)Bu, the compound (2) behaves as a simple paramagnet, with no magnetic interaction between individual Cr(III) centres along the whole temperature range measured (1.8-265 K). By contrast, a weak antiferromagnetic interaction is detected for compound 3 at low temperature with T(N) = 0.19(1) K. Since the closest intermetallic distances are similar in the crystals of 2·CH(2)Cl(2) and 3·1.75CH(2)Cl(2) (ca. 1.1 nm), we conclude that the insaturation of the aromatic Xy group together with the extended intermolecular π-π stacking interactions between Xy rings observed in the crystal lattice of 3·1.75CH(2)Cl(2) (centroid-to-centroid distance: 0.35 nm) favour magnetic interaction between the individual magnetic centres.     

Reassignment of the Configuration of Several Keto-cyclolignans Prepared from Podophyllotoxin

The configuration of several keto-cyclolignans related to podophyllotoxin has been reviewed. Under basic catalysis, the configuration at the C-atom in α-position to the lactone carbonyl group in podophyllotoxone is inverted instead of the C-atom in α-position to the ketone group, as it has been reported.     

Sufficiency and fuzziness in random experiments

In previous papers, the consequences of the “presence of fuzziness” in the experimental information on which statistical inferences are based were discussed. Thus, the intuitive assertion «fuzziness entails a loss of information» was formalized, by comparing the information in the “exact case” with that in the “fuzzy case”. This comparison was carried out through different criteria to compare experiments (in particular, that based on the “pattern” one, Blackwell's sufficiency criterion). Our purpose now is slightly different, in the sense that we try to compare two “fuzzy cases”. More precisely, the question we are interested in is the following: how will different “degrees of fuzziness” in the experimental information affect the sufficiency? In this paper, a study of this question is carried out by constructing an alternative criterion (equivalent to sufficiency under comparability conditions), but whose interpretation is more intuitive in the fuzzy case. The study is first developed for Bernoulli experiments, and the coherence with the axiomatic requirements for measures of fuzziness is also analyzed in such a situation. Then it is generalized to other random experiments and a simple example is examined.     

Conformational flexibility of a synthetic glycosylaminoglycan bound to a fibroblast growth factor. FGF-1 recognizes both the (1)C(4) and (2)S(O) conformations of a bioactive heparin-like hexasaccharide

The first direct NMR determination of the conformation of a conformationally flexible heparin-like hexasaccharide bound to a key receptor, FGF-1, is described. The determination has been based on the use of a 13C-labeled protein and a regular 12C sugar. FGF-1 recognizes several conformations of the iduronic moieties of the hexasaccharide. Therefore, this case is different than that described for the controversial recognition of heparin-like saccharides by AT-III, which seems to recognize just one conformation of the iduronic acid residues.     

Percolation and epidemic thresholds in clustered networks

We develop a theoretical approach to percolation in random clustered networks. We find that, although clustering in scale-free networks can strongly affect some percolation properties, such as the size and the resilience of the giant connected component, it cannot restore a finite percolation threshold. In turn, this implies the absence of an epidemic threshold in this class of networks, thus extending this result to a wide variety of real scale-free networks which shows a high level of transitivity. Our findings are in good agreement with numerical simulations.     

A new family of oxide ion conductors based on tricalcium oxy-silicate

Tricalcium oxy-silicates, Ca3(SiO4)O and Ca2.93Mg0.07(Si0.98Al0.02O4)O0.99 [square]0.01, have been prepared as crystalline single phases. Ca3(SiO4)O and Ca2.93Mg0.07(Si0.98Al0.02O4)O0.99 [square]0.01 have triclinic and monoclinic structures, respectively. The samples show oxide anion conductivity with a small p-type electronic contribution under oxidizing conditions. At 1023 K, the oxide transport numbers range between 0.97 and 0.85 from reducing (dry 5%-H2-Ar/air gradient) to oxidizing (O2/air gradient) conditions in the 1023-1173 K interval. The thermal analyses showed a large weight loss on heating due to the presence of water in the materials. The monoclinic compound has ionic conductivities higher than those of the triclinic stoichiometric oxy-silicate, as expected due to the introduction of oxide vacancies. Typical total conductivities for these un-optimised solids are 10(-5)-10(-4) S cm(-1) at 1100 K. These compounds may contain a small amount of water, approximately 0.05 H2O moles per chemical formula, and they display an important proton contribution under a humidified atmosphere.