Structure of 16-hydroxyisosteviol-derived dicarboxylic acid esters

Dielcometry, method of dipole moments, IR spectroscopy, and computer simulation were used to show that dicarboxylic acid esters derived from 16-hydroxyisosteviol (ent-16-hydroxybeyeran-19-oic acid) exist in CCl₄ solutions as tweezer-like or open-chain structures, or dimers with various steric structures, depending on the degree of dilution. Concentrations at which both the esters and parent dicarboxylic acids undergo structural rearrangement were established. The structure of three esters was confirmed by X-ray diffraction.     

Perrhenate and pertechnetate anion recognition properties of cyclo[8]pyrrole

Cyclo[8]pyrrole, an octapyrrolic expanded porphyrin with no meso-linking atoms, was found to interact with a series of anions in the solid state and in a chloroform solution. The anion selectivities have been determined relative to a structurally characterised salt, H₂cyclo[8]pyrrole²⁺·I^? ·I^3 ? , via counter anion exchange. Although cyclo[8]pyrrole demonstrates a general selectivity for sulfate, it interacts well with both the pertechnetate and perrhenate anions. Moreover, it has been shown to act as a phase-transfer catalyst facilitating the extraction of pertechnetate from an aqueous to an organic phase in the presence of sulfate.     

New dinuclear nickel(II) complexes: synthesis, structure, electrochemical, and magnetic properties

The reaction of [NiBr(2)(bpy)(2)] (bpy = 2,2'-bipyridine) with organic phosphinic acids ArP(O)(OH)H [Ar = Ph, 2,4,6-trimethylphenyl (Mes), 9-anthryl (Ant)] leads to the formation of binuclear nickel(II) complexes with bridging ArP(H)O(2)(-) ligands. Crystal structures of the binuclear complexes [Ni(2)(μ-O(2)P(H)Ar)(2)(bpy)(4)]Br(2) (Ar = Ph, Mes, Ant) have been determined. In each structure, the metal ions have distorted octahedral coordination and are doubly bridged by two arylphosphinato ligands. Magnetic susceptibility measurements have shown that these complexes display strong antiferromagnetic coupling between the two nickel atoms at low temperatures, apparently similar to binuclear nickel(II) complexes with bridging carboxylato ligands. Cyclic voltammetry and in situ EPR spectroelectrochemistry show that these complexes can be electrochemically reduced and oxidized with the formation of Ni(I),Ni(0)/Ni(III) derivatives.     

Synthesis and antimicrobial activity of several bis-quaternized ammonium derivatives of the diterpenoid isosteviol

Previously unreported bis-quaternized ammonium derivatives of the diterpenoid isosteviol (16-oxo-entbeyeran-19-oic acid) were synthesized. The compound in which the two quaternized N atoms were joined by a dodecamethylene spacer had the greatest antimicrobial activity and was comparable in activity with ciprofloxacin and clotrimazole.     

Antonina Nikolaevna Grafova

Obituary

Antonina Nikolaevna Grafova     

Synthesis and Biological Activity of Alkane-1,1-diylbis(phosphonates) of Diterpenoid Isosteviol

Russian Journal of Organic Chemistry - Isosteviol reacted with α,ω-dibromoalkanes to give 19-(ω-bromoahkyl) esters which were treated with tetraethyl methylenebis(phosphonate) to...     

Phosphorylated Glycoconjugates Based on Isosteviol,d-Arabinofuranose,and d-Ribofuranose

Russian Journal of Organic Chemistry - First phosphorylated glycoconjugates were synthesized in three stages on the basis of isosteviol, d-arabinofuranose, and d-ribofuranose. In the first stage,...     

Synthesis of novel 1,2,3-triazolyl nucleoside analogues bearing uracil, 6-methyluracil, 3,6-dimethyluracil,thymine, and quinazoline-2,4-dione moieties

A series of novel 1,2,3-triazolyl nucleoside analogues was synthesized via the CuAAC reaction of N1-alkynyl uracil, 6-methyluracil, 3,6-dimethyl uracil, thymine and quinazolin-2,4-dione with protected azido β-d-ribofuranose. The obtained compounds differ in both the nature of the pyrimidine-2,4-dione fragment and the length of the polymethylene linker connecting it with the β-d-ribofuranosyl-1,2,3-triazol-4-yl moiety. The 1,2,3-triazolyl nucleoside analogues were evaluated for their cytotoxicity in vitro.     

Estimate of the Degree of the Spin Polarization of a Ferromagnet from Data on the Superconductor/Ferromagnet Proximity Effect

The superconductor/ferromagnet proximity effect in the Pb/Co₂Cr_1–xFe _x Al bilayer systems has been studied. Thin films of the Heusler alloy Co₂Cr_1–xFe _x Al have been prepared at different substrate temperatures. It has been established using Andreev spectroscopy of point contacts that the degree of spin polarization of conduction electrons in the Heusler alloy is on the order of 30 and 70% for the films prepared at a substrate temperature of 300 and 600 K, respectively. It has been found that the dependence of the superconducting transition temperature on the thickness of the Pb layer at a fixed thickness of the Heusler layer is determined by the degree of spin polarization of the conduction band in the ferromagnetic layer.     

Dependence of Five- and Six-Loop Estimated QCD Corrections to the Relation between Pole and Running Masses of Heavy Quarks on the Number of Light Flavors

JETP Letters - Various theoretical approaches are used to determine the dependence of the estimated x O(αs5) and O(αs6)-corrections to the quantum chromodynamics relation between pole and...