Synthesis and stereochemistry of 8-methyl-5-nitro-1-octalones

Summary Base catalyzedMichael addition of 5-nitropentan-2-one ethylene ketal (1) and cyclohex-2-enone (2), subsequent deprotection, and intramolecular aldol condensation yields the 8-methyl-5-nitro-1-octalone isomers (5a,b). The structure, relative configuration, and conformation of5a and5b were elucidated utilizing the results of¹H and¹³C NMR investigations

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Synthese und Stereochemie von 8-Methyl-5-nitro-octalonen

Zusammenfassung BasenkatalysierteMichael-Addition von 5-Nitropentan-2-on-ethylenketal (1) und Cyclohex-2-enon (2), anschließende Entfernung der Schutzgruppe und darauffolgende Aldolkondensation liefert isomer 8-Methyl-5-nitro-1-octalone (5a,b). Struktur, relative Konfiguration und Konformation von5a und5b wurden mittels¹H- und¹³C-NMR-Spektroskopie aufgeklärt.

     

Charge reduction in a vermiculite by acid and hydrothermal methods: a comparative study

A comparative study on acid and hydrothermal methods as ways to reduce interlamellar charge has been carried out on a vermiculite. This study showed that the application of the hydrothermal treatment as a previous step to pillaring the vermiculites, reported here for the first time, is a new route to obtain the porous material with a particular interest as heterogeneous catalysts, starting from mineral clays with a high density of charge. Modified clays have been characterized by atomic absorption, emission spectrograph, X-ray diffraction, cation-exchange capacity, total acidity, infrared spectroscopy (DRIFT), and nitrogen adsorption. The results have shown that all solids have been structurally modified. However, acid and hydrothermal methods showed different behavior. For the vermiculite, the hydrothermal treatment did not produce major differences in terms of the crystalline structure, whereas the acid method caused severe structural damage. The catalytic properties have been tested over Pt-impregnated samples (1%) using the hydroisomerization of heptane. Important catalytic activity was established for all solids with high selectivity regarding the isomer products.     

Mutarotation and isomerization of imines. Substituted N-(1-phenylethyl)-1-benzoylbenzylideneimines.

The mutarotation observed for several benzilmonoimines, having a chiral center, is atributed to the equilibration between two stereoisomers which differ in configuration around the single bond OCCN which, due to restricted rotation, becomes a chiral axis of the imines.     

Preliminary results of layer chromatography combined with bilateral band compression to search active minor components

Abstract

Bilateral band compression (BBC) is a process where a solvent flow perpendicular to the direction of development squeezes bands into a smaller area. BBC of the 10 mm wide lanes of high-performance thin-layer chromatography (HPTLC) separation resulted in more than 6 times increase in peak height and peak area of Canadian goldenrod labdane diterpenes solidagenone and presolidagenone. Simultaneously, the signal-to-noise ratio increased only up to 2.2–2.4 times due to the higher noise level. The BBC increased the relative standard deviations (RSDs) of peak height and area reached three to four times of the original as well. It is known that overpressured layer chromatography (OPLC) separates more efficiently than conventional TLC/HPTLC techniques. In order to increase the bio-detection sensitivity, we combined bioautography, BBC, and fully offline infusion-OPLC using band-shaped sample application/separation. Thyme essential oil has been applied as a multi-component object to show the potential of this process. It is demonstrated that biologically active minor components, which may be missed in case of a conventional process, can also be detected by means of this combined method.     

Chemical Modifications on Human Hair Studied by Means of Contact Angle Determination

Wetting properties of a solid surface can change as a consequence of chemical treatment. There is a relationship between the molecular structure of a surface and the macroscopic properties of this surface such as wetting and adhesion. Information on the surface energy of a solid was obtained by calculating polar and dispersion force contributions by means of contact angle determination. The superficial modification undergone by human hair treatments with or without hydrogen peroxide at alkaline pH was studied by means of wetting force measurements. The wetting increase in treated human hair fibers was analyzed following the Hüttinger method using contact angle data, taking into account the acid-base and dispersion components of the total wetting adhesion work. The hydrogen peroxide treatment at alkaline pH leads to a partial removal of hydrocarbon chains and to the formation of ionic groups (cysteic acid residues) on the outer scale cell surface. The latter phenomenon was observed by means of an increase in the acid-base adhesion work versus water wetting liquid at alkaline pH. Copyright 2001 Academic Press.     

Applications of Laser-Raman spectroscopy to the analysis of polynucleotides containing uridine residues

Summary Qualitative characterization of uridine C(2)-endo-anti and C(3)-endo-anti forms has been carried out for the first time using Laser-Raman spectroscopy. Spectra are presented for some crystals containing the uridine residue whose conformations are known from their X-ray crystallographic analyses. Crystalline uridine and uridine 5-monophosphate as its lithium, sodium, potassium, barium and cadmium salts give Raman bands in the 600–700 cm^–1 range that seem to reflect sensitively and regularly the conformation of the uridine residue and, therefore, are proposed as convenient indicators of the above structures. A method for the determination of the uridine C(2)-endo-anti form in polyribonucleotides is also described. The usefulness of these characterizations in the conformational analysis of polyribonucleotides is shown.     

MIP models for production lot sizing problems with distribution costs and cargo arrangement

This study presents mixed integer programming (MIP) models for production lot sizing problems with distribution costs using unit load devices such as pallets and containers. Problems that integrate production lot sizing decisions and loading of the products in vehicles (bins) are also modelled, in which constraints such as weight limits, volume restrictions or the value of the cargo loaded in the bins are considered. In general, these problems involve a trade-off between production, inventory and distribution costs. Lot sizing decisions should take into account production capacity and product demand constraints. Distribution decisions are related to the loading and transport of products in unit load devices. The MIP models are solved by the branch-and-cut method of an optimization package and the results show that these approaches have the potential to address different practical situations.     

Close‐to‐convexity of normalized Dini functions

In this paper necessary and sufficient conditions are deduced for the close‐to‐convexity of some special combinations of Bessel functions of the first kind and their derivatives by using a result of Shah and Trimble about transcendental entire functions with univalent derivatives and some newly discovered Mittag–Leffler expansions for Bessel functions of the first kind.     

Rolling Against a Sphere: The Non-transitive Case

We study the control system of a Riemannian manifold M of dimension n rolling on the sphere \(S^n\). The controllability of this system is described in terms of the holonomy of a vector bundle connection which, we prove, is isomorphic to the Riemannian holonomy group of the cone C(M) of M. Using Berger’s list, we reduce the possible holonomies to a few families. In particular, we focus on the cases where the holonomy is the unitary and the symplectic group. In the first case, using the rolling formalism, we construct explicitly a Sasakian structure on M; and in the second case, we construct a 3-Sasakian structure on M.