2,3-dimethoxyperhydro-1,4,2,3-dioxadiazine: Synthesis,conformation, and conversion to 1-(2-hydroxyethoxy)-2-methoxydiazene-1-oxide. Crystal structure of 1-[2-(para-nitrobenzoyloxy)-ethoxy]-2-methoxydiazene-1-oxide

The oxidation of 1,2-bis(methoxyaminooxy)ethane (3) with PbO₂ afforded 2,3-dimethoxyperhydro-1,4,2,3-dioxadiazine (4) in the form of the 55:45 mixture of thetrans-4ee- andcis-4 isomers. The barrier of the ring conversion (G₂₃₈ =11.3 kcal/mole) of thecis-4 isomer was determined by the method of¹³C NMR. The regio- and stereospecific stereoelectronically controlled reaction of (4) withpara-nitrobenzoic acid gives the equimolar mixture of methylpara-nitrobenzoate and the 1,2-dialkoxydiazene oxide (5), the structure of which, and the (E)-configuration, were shown by the x-ray structural data of its acylation product — the diazene oxide (6).N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2624–2632, November, 1992.     

Atomic absorption spectroscopic investigation of the mineral fraction of pectins obtained from pumpkin and sugar beet

Summary Data on the mineral composition of plant cell wall carboxypolysaccharides (pectins), obtained from non-traditional vegetable sources (pumpkin and sugar beet) using a biotechnological process of enzymatic extraction (biopectin) and the traditional method of acid treatment, are presented. The results have been obtained by flame (FAAS) or graphite furnace atomic absorption spectroscopy (GFAAS) and include trace analyses of the heavy metal content. It is shown that biopectin has an unusually high total mineral content, due mainly to markedly increased contents of Ca and Mg. The content of a series of alkaline, alkaline earth, and heavy metals in the pectins is compared considering the effect of the extraction method.

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Atomabsorptionsspektroskopische Untersuchung des Mineralanteils von Pektinen aus Kürbissen und Zuckerrüben

Zusammenfassung Die Zusammensetzung des mineralischen Anteils von Carboxypolysacchariden (Pektinen), die mittels eines biotechnologischen Prozesses (enzymatische Extraktion; Biopektin) bzw. der üblichen Methode (Behandlung mit Säure) aus den Zellwänden von Pflanzen (Kürbis, Zuckerrübe) gewonnen wurden, wird diskutiert. Die Ergebnisse wurden mittels Flammenatomabsorptionsspektroskopie (FAAS) oder im Graphitofen (GFAAS) bestimmt und beinhalten Spurenanalysen des Schwermetallgehalts. Es wird gezeigt, daß Biopektin einen unüblich hohen Mineralanteil aufweist, der hauptsächlich auf den hohen Gehalt an Ca und Mg zurückzuführen ist. Der Gehalt an einer Reihe von Alkali-, Erdalkali- und Schwermetallen wird verglichen und zur Isolationsmethode der Pektine in Beziehung gesetzt.

     

Synthesis of 20-hydroxyecdysone 25-acetate

A scheme has been developed for the selective conjugation of 20-hydroxyecdysone (20E) at the 25- position, with the synthesis of 20E 25-acetate as an example. The proposed scheme also permits the selective, synthesis of 20E 22-esters from both lower and higher fatty acids, which opens up prospects for the creation from them of drugs with a prolonged action.Institute of Biology, Komi Scientific Center, Urals Division of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, Vol. 33, No. 1, pp. 74–78, January–February, 1977.     

Anisotropy‐assisted non‐scattering coherent absorption of surface plasmon‐polaritons

The ability to control propagation of electromagnetic guided modes lies at the heart of integrated nanophotonics. Surface plasmon‐polaritons are a class of guided modes which can be employed in integrated optical systems. Here, we present a theoretical design of a coherent surface plasmon absorber which can perfectly harvest energy of coherently incident surface plasmons without parasitic scattering into free space modes. Excitation of free space modes which usually accompanies scattering of a surface plasmon by an interface boundary is avoided due to specially tailored anisotropy of the absorber. The concept of coherent SPP absorber is analyzed numerically for spatially non‐uniform and finite‐size structures. We believe that our results will be important for the development of integrated nanoplasmonic systems.     

Semiempirical calculation of two-electron integrals using bipolar expansion of the Ohno potential

Bipolar expansion of the Ohno potential as a method of calculating two-center Coulomb integrals that appear in the NDDO approximation is generalized to one-center two-electron integrals. A unified semiempirical scheme is suggested for estimating two-electron interactions in molecules. This scheme can be readily extended to arbitrary Slater basis sets (including the s,p,d-orbitals) and involves no a priori data on the valent states of atoms. In this work, the scheme is employed to extend the semiempirical PM3 method to the s,p,d-basis set. The efficiency of the method is proven by test calculations of 24 chromium compounds (π-complexes, carbonyls, isocyanides, etc.). Scientific Research Institute of Chemistry at N. I. Lobachevskii Nizhnii Novgorod State University. Translated fromZhurnal Struktumoi Khimii, Vol. 36, No. 4, pp. 593–599, July–August, 1995. Translated by I. Izvekova.     

Procedures for the calculation of leakproof butt joints

An algorithm is presented for plotting dependences that make it possible to predict the possibility sealing of joints with hot-melt adhesives. The effect of a surface treatment on the character of the dependences is considered. Recommendations are given concerning the determination of optimal technological parameters of joints.