Hetero-diels-alder reaction of enaminecarbaldehydes an entry to branched aminosugars

N-acyl-enaminecarbaldehydes 6a - g with an electron accepting group in the α- position react in a hetero-Diels-Alder cycloaddition with enolethers 7a - g to 4-amino- dihydropyrans 8a - g, 9a - g and 10a - g. This reaction represents a convenient entry to branched aminosugars of the garosamine-type. The rate of the cycloaddition depends strongly on the N-acyl group in 6. However, the phthalimide 11 does not react because of deconjugation of the electron accepting function in the α-opposition.     

Isotope effects and the nature of stereo- and regioselectivity in hydroaminations of vinylarenes catalyzed by palladium(ii)-diphosphine complexes

[reaction: see text] The hydroamination of styrene with aniline catalyzed by phosphine-ligated palladium triflates exhibits a substantial (13)C isotope effect at the benzylic carbon. This supports rate-determining nucleophilic attack of amine on a eta(3)-phenethyl palladium complex. Deuterium exchange observations and predicted isotope effects based on DFT calculations support this mechanism. Selectivity in these reactions is determined by the facility of palladium displacement after reversible hydropalladation of the alkene.     

Integration theory for Hammerstein operators

We develop in this article a strong nonlinear integral and obtain a Riesz-type theorem (utilizing this integral) for the class of (nonlinear) Hammerstein operators. The integral is extended to the class $\text{M}$_E($\text{B}$) of E-valued totally $\text{B}$-measurable functions and convergence theorems are studied. Then an exchange of information is carried out between the operators and the corresponding set functions; for example, the implication of the operator being compact or unconditionally summing is drawn. In the latter case it is shown that the representing set function is analogous to strongly bounded set functions. A vast body of literature exists for both of these concepts.     

Looking Ahead with the Pilot Method

The pilot method as a meta-heuristic is a tempered greedy method aimed at obtaining better solutions while avoiding the greedy trap by looking ahead for each possible choice. Repeatedly a master solution is modified; each time in a minimal fashion to account for best choices, where choices are judged by means of a separate heuristic result, the pilot solution. The pilot method may be seen as a meta-heuristic enhancing the quality of (any) heuristic in a system for heuristic repetition. Experiments show that the pilot method as well as similar methods can behave quite competitively in comparison with well-known and accepted meta-heuristics. In this paper we review some less known results. As a higher time complexity is usually associated with repetition, we investigate a simple short-cut policy to reduce the running times, while retaining an enhanced solution quality. Furthermore, we report successful experiments that incorporate a distinguishing feature of the pilot method, which is the extension of neighborhoods into “local” search, creating tabu search hybrids.     

Crystal and molecular structure of di(1-pyrazolyl)methane,CH2(C3N2H3)2

The title compound consists of two planar pyrazolyl fragments oriented at 73.0° to each other and linked to a common carbon atom. All hydrogen atoms were located unambiguously and their positions were refined.     

New method for processing gamma backscattering spectra to estimate saturation depth and to determine thickness of aluminum and steel materials

In this study, we present a new gamma spectrum processing method is applied to analyze experimental scattering spectra on aluminum and steel for determining the intensity of the single scattering component. Based on these results, the saturation depth of aluminum and steel materials are 78.8 and 22.5 mm, respectively. The thickness of both materials is determined with a maximum relative deviation of about 7% in comparison with real thickness. Besides, the result also shows that we can use the new spectrum processing method, which is a simple, and useful solution to determine the material thickness, for NaI(Tl) detector and a low activity source.     

Diversity of the surface properties of Lactococci and consequences on adhesion to food components

Bacteria possess surface properties, related to their charge, hydrophobicity and Lewis acid/base characteristics, that are involved in the attachment processes of microorganisms to surfaces. Fermentation bulks and food matrixes are complex heterogeneous media containing various components with different physicochemical characteristics. The aim of the present study was to investigate whether (i) bacteria present in a food matrix, interacted physicochemically at their surface level with the other constituents and (ii) the diversity of bacterial surface properties could result in a diversity of microbial adhesion to components and thus in a diversity of tolerance to toxic compounds. The surface properties of 20 lactic acid bacteria were characterized by the MATS method showing their relatively hydrophilic and various basic characteristics. The results obtained from a set of representative strains showed that (i) the strains with higher affinity for apolar solvents adsorbed more to lipids and hydrophobic compounds, (ii) the more the strains adsorbed to a toxic solvent, the less they were tolerant to this solvent. A diversity of bacterial surface properties was observed for the strains in the same species showing the importance of choosing bacteria according to their surface properties in function of technological objectives.     

A few molecules can control the enantiomeric outcome. Evidence supporting absolute asymmetric synthesis using the Soai asymmetric autocatalysis

[reaction: see text] Experiments were carried out to investigate whether the Soai asymmetric autocatalysis can accomplish true absolute asymmetric synthesis. In 54 reactions, R and S enantiomeric products were obtained 27 times each. Of 25 pairs of side-by-side identical reactions, 12 afforded opposite enantiomers. In a test of the mechanistic viability of a random-chance process, it was found that a very few molecules (approximately 60 000) were sufficient to control the enantiomeric outcome of these reactions. These observations appear most consistent with asymmetric synthesis originating from the chance enantiomeric excess in a racemate.