Through-space electrostatic control in a novel regiospecific ring transformation of 1,3,4-trisubstituted maleimides

Ring transformation of 1-ethoxycarbonyl-3,4-disubstituted maleimide in alkaline solution yielded exclusively 1,5-disubstituted orotic acid. No hydantoin derivatives were detected. These findings can be best explained by assuming that the initial attack of the hydroxylate anion occurs at C2 and not at C5. X-ray diffraction and quantum chemical investigations indicate that stereospecificity is mainly due to through-space electrostatic effects.     

Kinetic analysis of TG data XXXVI: Influence of procedural variables upon the apparent kinetic parameters of the thermal deamination

A number of 7 complexes of the [Co(DH)₂(amine)₂)]I type (DH₂ stands for dimethyloxime) have been studied by means of thermogravimetry and differential scanning calorimetry in nitrogen atmosphere, by using heating rates of 2.5, 5 and 10 K min^–1. In all cases an endothermal deamination reaction occurs leading to the relatively stable [Co(DH)₂I(amine)] intermediate. For this reaction apparent kinetic parameters have been derived. The influence of heating rate is discussed. The validity of a linear and a non-linear kinetic compensation law was verified.This revised version was published online in November 2005 with corrections to the Cover Date.     

Influence of fadA G203R and ΔflbA mutations on morphology and physiology of submerged Aspergillus nidulans cultures

Morphologic and physiologic changes taking place in carbon-limited submerged cultures of Aspergillus nidulans ΔflbA and fadA ^G203R strains were studied. Loss-of-function mutation of the flbA gene resulted in an altered germination with unusually thick germination tubes, “fluffy” pellet morphology, as well as a reduced fragmentation rate of hyphae during autolysis. In the fadA ^G203R mutant strain, conidiophores formed in the stationary phase of growth, and the size of pellets shrank considerably. There were no significant differences in the generation of reactive oxygen species (ROS) and in the specific catalase and superoxide dismutase activities by the tested mutants and the appropriate parental strains. Therefore, the participation of ROS or antioxidative enzymes in FadA/FlbA signaling pathways seems to be unlikely in submerged cultures. On the other hand, earlier increases in the extracellular protease and ammonia production were recorded with the ΔflbA strain, whereas the protease and ammonia production of the fadA ^G203R mutant lagged behind those of the wild-type strains. Similar changes in the time courses of the induction of γ-glutamyltranspeptidase and the degradation of glutathione were observed. These results suggest that FadA/FlbA signaling may be involved in the mobilization of protein and peptide reserves as energy sources during carbon starvation.     

Structural and temperature effects in the high-performance liquid chromatographic enantioseparation of 1-(alpha-aminobenzyl)-2-naphthol and 2-(alpha-aminobenzyl)-1-naphthol analogs

The enantiomers of 1-(alpha-aminobenzyl)-2-naphthol and 2-(alpha-aminobenzyl)-1-naphthol analogs were separated isothermally on a cellulose-tris-3,5-dimethylphenyl carbamate-based chiral stationary phase (Chiralcel OD-H), at 10 degrees C increments in the range of 5-35 degrees C, using n-hexane/2-propanol/diethylamine as mobile phase. The mobile phase composition and temperature were varied to achieve baseline resolutions in a single chromatographic run. The dependence of the natural logarithms of selectivity factors, In alpha, on the inverse of temperature, 1/T, was used to determine the thermodynamic data of the enantiomers. The thermodynamic data revealed that all the compounds in this study separate via the same enthalpy-driven chiral recognition mechanism.     

Enthalpic Relaxation of 25Na2O·xTiO2·(75-x)SiO2 Glasses

The enthalpic relaxation of the title glasses, studied by differential scanning calorimetry, is well described by a mathematical model based on the stretched exponential relaxation function with the relaxation time proportional to the actual viscosity. The dependence of viscosity on temperature and the fictive temperature was expressed by Mazurin's approximation. The relaxation parameters obtained correlated significantly with the glass composition, indicating the changes in the structural of the TiO₂ role near a TiO₂ content of 3–4 mol%. This revised version was published online in August 2006 with corrections to the Cover Date.     

A simplified multidimensional integral

We present a simplified integral of functions of several variables. Although less general than the Riemann integral, most functions of practical interest are still integrable. On the other hand, the basic integral theorems can be obtained more quickly. We also give a characterization of the integrable functions and their primitives.     

Efficient and selective hydration of nitriles to amides in aqueous systems with Ru(II)-phosphaurotropine catalysts

A simple and efficient synthesis of amides by selective hydration of aromatic and aliphatic nitriles is described. The catalysts are prepared in situ from easily available Ru-precursors and ligands using water as the solvent. The most active catalyst, is obtained from [RuCl₂(dmso)₄] and benzylated 1,3,5-triaza-7-phosphaadamantane. Of the 16 substrates examined, 92–99% conversions of 14 nitriles were achieved in one hour at reflux temperature.     

Self‐association promoted conformational transition of (3R,4S,8R,9R)‐9‐[(3,5‐bis(trifluoromethyl)phenyl))‐thiourea](9‐deoxy)‐epi‐cinchonine

The conformational diversity of the (3R,4S,8R,9R)‐9‐[(3,5‐bis(trifluoromethyl)phenyl))‐thiourea](9‐deoxy)‐epi‐cinchonine organocatalyst is discussed. Low‐temperature NMR experiments confirmed a self‐association process, which promotes the quinoline rotation between two intramolecularly hydrogen‐bonded monomeric conformers of the catalyst. The balanced population of the coexisting monomeric and dimeric species allowed us to conduct a structural study of a rather complex conformational dynamics of the pure catalyst. The study is extended by a comparison with other members of the bifunctional amine‐thiourea organocatalyst family. Changes in the molecular structure of the catalysts influence the interplay between intra‐ and intermolecular hydrogen bonding, and yield different extent of catalyst self‐association. By assessing the conformation of the individual states, we established the thermodynamic model of a self‐association promoted conformational transition. Copyright © 2009 John Wiley & Sons, Ltd.     

Generalized Monotone Operators on Dense Sets

In the present work we show that the local generalized monotonicity of a lower semicontinuous set-valued operator on some certain type of dense sets ensures the global generalized monotonicity of that operator. We achieve this goal gradually by showing at first that the lower semicontinuous set-valued functions of one real variable, which are locally generalized monotone on a dense subsets of their domain are globally generalized monotone. Then, these results are extended to the case of set-valued operators on arbitrary Banach spaces. We close this work with a section on the global generalized convexity of a real valued function, which is obtained out of its local counterpart on some dense sets.