2-{(4a′S,6a′S,10a′R,10b′R)-Octahydrospiro[1,3-dioxolane-2,2′-pyrano[2,3-c]chromen]-6a′(1′H)-yloxy}ethanol in the Synthesis of (2S)- and (2R)-Dodecane-1,2-diols

Russian Journal of Organic Chemistry - Michael adduct of levoglucosenone and cyclohexanone, 1,6-anhydro-3,4-dideoxy-4-C-(2-oxocyclohexan-1-yl)-β-D-erythrohexo-2-ulose, was treated with...     

Synthesis and Halocyclization of 5-Allyl-2-benzyl(allyl)sulfanyl-6-methylpyrimidin-4(3H)-ones

Russian Journal of Organic Chemistry - Alkylation of 5-allyl-6-methyl-2-thiouracil with benzyl chloride and allyl bromide afforded 2-benzyl(allyl)sulfanyl-5-allyl-6-methylpyrimidin-4(3H)-ones....     

Synthesis and Aminoalkylation of N-Propargyl Triterpene Aldimines

Russian Journal of Organic Chemistry - Mannich reaction of N-propargyl triterpene aldimines obtained from betulonic and oleanonic aldehydes gave new aminoalkyl derivatives containing an...     

AFM observation of a retgersite crystal surface growing in a water-ethanol solution

In situ investigation of the growth and dissolution of retgersite crystals α-NiSO₄ · 6H₂O in water-ethanol solutions (10–50 wt % of ethanol) was made by atomic force microscopy (AFM). The habit of crystals grown in aqueous and water-ethanol solutions, as well as the Raman scattering spectra, were identical. It is shown that the typical peak of sulphate ions at 981 cm⁻¹ does not change after the addition of ethanol. Absorption spectra of aqueous and water-ethanol solutions also have similar characteristic features. AFM images of hillocks on the (001) face of retgersite crystals were obtained directly in the process of their growth. Using a series of distorted AFM images obtained in situ, a geometrical calculation scheme is given, which allows one to recover the real direction of the growth steps. The kinetic coefficient of growth steps in aqueous and water-ethanol solutions of retgersite is estimated.     

X-ray amplification in intense ultrashort KrF laser–Xe cluster interactions

In earlier work, a time-dependent, ionization dynamic model of a cluster of xenon atoms was constructed [2], [3] in an effort to determine conditions under which the X-ray line amplification data that was observed experimentally at wavelengths between 2.71 and 2.88 Å [1] could be replicated. Model calculations showed that, at laser intensities greater than 10¹⁹ W/cm², the outermost N-shell electrons of xenon would be stripped away by tunnel ionization in less than a femtosecond. They also showed that L-shell electrons within the resulting cluster of Ni-like ions could be photoionized at a sufficient rate as to generate population inversions between these hole states and the states they radiatively decayed into. These inversions only lasted for several femtoseconds, and they were generated early in time when the cluster was being rapidly heated and the cluster's density was rapidly evolving, but was still high. They were seen to depend on the heating and expansion dynamics of the cluster, which had not been modeled in detail in this early work. In this paper, molecular dynamics calculations are described in which the rapidly evolving temperatures and ion densities of an intensely laser-heated cluster are calculated for different peak laser intensities and for two different sized xenon nano-clusters. This data is then used as an input to the ionization dynamic calculations in order to determine the influence of cluster size and of peak laser intensity on the gain coefficient calculations. In these calculations, inner-shell photoionization rates are shaped by the temperature and density dependence of the bremsstrahlung emissions under the assumption that these emissions drive the photoionizations. This shaping produces calculated gain coefficients that agree well with the measured ones.     

REACTION OF LITHIUM DERIVATIVE OF DIETHYL PHENYLMETHANE-PHOSPHONATE WITH KETONES

Abstract

The reaction of the lithium derivative of diethyl ester of phenylmethanephosphonic acid (1-Li) with alkanones, cycloalkanones, alkylaryl and diarylketones 2s-b is studied at -70°C in THF. The corresponding adducts-diethyl esters of l-phenyl-2,2-dialkyl(phenyl)-2-hydroxyethanephosphonic acids 3s-h are isolated, their yields being usually higher at short reaction time. The olefination of 3-Li as well as of 3 (both by thermolysis or in acidic media) proceeds in low degree, while in the case of 3-Na the yields of alkenes 4 are good. The relative configurations of 3b. 31 and 3g are determined by IR and NMR-spectra, as well as by their stereospecific olefination. “Threo”-stereoselectivity of the addition stage of the reaction of 1-Li with 2b, 21 and 2g is observed, the “threo”/“erythro” ratio remaining independent on the reaction time.     

Synthesis and biological activity of dialkylamino-substituted phosphine oxides

A series of dialkylamino-substituted phosphine oxides was synthesized and their physiological activity was studied.     

New possibilities of X-ray nanocrystallography of biological macromolecules based on X-ray free-electron lasers

X-ray serial nanocrystallography is a new technique for determining the three-dimensional structure of biological macromolecules from data on the diffraction of ultrashort pulses generated by X-ray free-electron lasers. The maximum achievable resolution for a set of experimental data as a function of the sample sizes and parameters of the equipment is estimated based on simulations of the diffraction process with allowance for changes in the electronic structure of the atoms of the sample under the influence of X-rays. Estimates show that nanocrystallography greatly enhances the possibilities of X-ray analysis, reducing the requirements for the minimum permitted size of the crystals and enabling to explore poorly crystallizable molecular objects, such as many membrane proteins and complexes of macromolecules.     

Modified fluororubbers based on SKF-26: Relaxation and mechanical properties

Samples of SKF-26 fluororubber modified by incorporating pendant methoxy groups into the macromolecular chain were studied by dielectric spectroscopy and dynamic mechanical analysis.