New approach to the synthesis of 4-amino-2-pyridone and 1-phenyl-1,6-naphthyridinone derivatives based on substituted 3-and 5-formyl-2-pyridones

The reactions of 3-cyano-3(5)-formyl-2-oxo-4-(phenylamino)-1,2-dihydropyridines with CH acids were studied. The previously unknown fused 2-pyridone derivatives containing the 4-aminopyridine fragment were synthesized by the Knoevenagel reaction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1416-1420, August, 2006.     

Structure of “furfuramide” and “furfurine”

The structures of ,-bis(furfurylideneimino)silvan (furfuramide or N,N'-difurfurylidene-2-furanmethanediamine) and the product of its thermal cyclization 2,4,5-tris (-furyl)-2-imidazoline (furfurine) were confirmed by comparison of the IR, UV, ¹H and ¹³C NMR, and mass spectra. It is shown that acetylation of the latter with acetic anhydride in the case of heating of the reagents without a solvent or in pyridine takes place with opening of the imidazoline ring and leads to the formation of 1,2-bis(-furyl)-1-acetamido-2-(-furoylamido)ethane.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1461–1464, November, 1978.     

Conformational analysis of 3-borabicyclo[3.3.1]nonane derivatives

Conformations of 3-borabicyclo[3.3.1]nonane derivatives have been studied by means of ¹H and ¹³C NMR spectroscopy. With the aid of the coupling constants ³J(HH) and ¹³C chemical shifts it has been shown that all the derivatives of 3-borabicyclo[3.3.1]nonane with the trigonal boron atom studied are in a flattened double-chair conformation. In 3-borabicyclo[3.3.1]nonane derivatives with the tetra-coordinated boron atom and substituents at the 7α-position, the chair-boat conformation predominates, the boat conformation being characteristic of the cyclohexane ring; exceptions are the compounds with the internal donor—acceptor bond between the boron atom an 7α-substituent.     

Triterpene glycosides ofHedera helix II. Determination of the structure of glycoside L-6d from common ivy leaves

A new hederagenin pentaoside — glycoside L-6d — has been isolated from the leaves of common ivyHedera helix L., fam. Araliaceae, and its structure has been determined by using various NMR-spectroscopic methods. Glycoside L-6d is hederagenin 3-O-[O--L-rhamnopyranosyl-(14)-O--D-glucopyranosyl-(16)-O--D-glucopyranosyl-(14)-O--L-rhamnopyranosyl-(12)--L-arabinopyranoside.Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 746–752, November–December, 1994.     

Synthesis of lipooligosaccharides related to nodulation factors ofRhizobium sp. NGR234

Trisaccharide analogs of natural nodulation factors fromRhizobium sp. NGR234, namely, 2-acetamido-2-deoxy-4-O-(2-deoxy-2-hexadecanamido-β-d-glucopyranosyl)-6-O-(2-O-methyl-α-l-fucopyranosyl)-d-glucopyranose and its derivatives containing a 4-O-acetyl or a 3-O-sulfo group at thel-fucose residue, were synthesized. The oligosaccharides synthesized were shown to posses biological activity. Laboratoire de Biologie Moléculaire des Plantes Supérieures (LBMPS), Université de Genève, 1 ch. de l'Impératrice, 1292 Chambesy-Genève, Suisse. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya No. 3, pp. 513–518, March, 1998.     

A finite volume cell‐centered Lagrangian hydrodynamics approach for solids in general unstructured grids

A finite volume cell‐centered Lagrangian hydrodynamics approach, formulated in Cartesian frame, is presented for solving elasto‐plastic response of solids in general unstructured grids. Because solid materials can sustain significant shear deformation, evolution equations for stress and strain fields are solved in addition to mass, momentum, and energy conservation laws. The total stress is split into deviatoric shear stress and dilatational components. The dilatational response of the material is modeled using the Mie‐Grüneisen equation of state. A predicted trial elastic deviatoric stress state is evolved assuming a pure elastic deformation in accordance with the hypo‐elastic stress‐strain relation. The evolution equations are advanced in time by constructing vertex velocity and corner traction force vectors using multi‐dimensional Riemann solutions erected at mesh vertices. Conservation of momentum and total energy along with the increase in entropy principle are invoked for computing these quantities at the vertices. Final state of deviatoric stress is effected via radial return algorithm based on the J‐2 von Mises yield condition. The scheme presented in this work is second‐order accurate both in space and time. The suitability of the scheme is evinced by solving one‐ and two‐dimensional benchmark problems both in structured grids and in unstructured grids with polygonal cells. Copyright © 2013 John Wiley & Sons, Ltd.     

Definitive Structural Assessment of Enterococcal Diheteroglycan

Enterococcus faecalis is one of most important nosocomial and often multi‐antibiotic resistant pathogens responsible for infections that are difficult to treat. Previously, a cell‐wall polysaccharide termed diheteroglycan (DHG) was isolated and characterized as a promising vaccine candidate. However, the configuration of its lactic acid (LA) residue attached to the galactofuranoside unit was not assessed, although it influences conformation of DHG chain in terms of biological recognition and immune evasion. This study proves the R configuration of the LA residue by means of chemical analysis, investigation of intramolecular NMR nuclear Overhauser effects and molecular dynamics simulations of native DHG and corresponding R and S models, which were obtained by using pyranoside‐into‐furanoside rearrangement. As alternative treatment and prevention strategies for E. faecalis are desperately needed, this discovery may offer the prospect of a synthetic vaccine to actively immunize patients at risk.     

Selectin Receptors 4: Synthesis of Tetrasaccharides Sialyl Lewis A and Sialyl Lewis X Containing A Spacer Group1,2

ABSTRACT

Synthesis of two isomeric tetrasaccharides, namely Neu5Acα(2→3)Galβ(1→3)[Fucα(1→4)GlcNAcβ (sLe^a) and Neu5Acα(2→3)Galβ(1→4)[Fucα(1→3)]GlcNAcβ (sLe^x) as 3-aminopropyl glycosides is described. Preparation of these compounds was performed by sialylation of selectively protected trisaccharides Le^a and Le^x which contain three unsubstituted OH groups at positions 2, 3 and 4 of Gal residue. Glycosylation of Le^x trisaccharide with ethylthio sialoside under promotion by NIS and TfOH in acetonitrile was effective and regio- and stereoselective to give sLe^x derivative in 81% yield. In contrast, sialylation of the Lc^a acceptor was accompanied by a variety of undesirable by-processes, namely. N-thioethylation of the GlcNAc residue, β-sialylation, and lactonisation. In order to improve the yield of sLc^a tetrasaccharide the glycosylation of Le^a acceptor by sialyl donors of ethyl and phenyl thioglycoside (promoted by NIS-TfOH or NBS-Bu₄NBr), xanthate (promotion by NIS-TfOH mixture or MeOTf) and phosphite (promoted by TMSOTf) types was also studied. Among the reactions investigated the glycosylation by phenyl thioglycoside sialoside promoted by NIS-TfOH gives the best yield (39%) of sLe^a tetrasaccharide product.     

Comprehensive Analysis of the Liquid Fraction of Car Tire Pyrolysis Products by Gas Chromatography–Mass Spectrometry

Russian Journal of Applied Chemistry - The liquid fraction of tire pyrolysis products was comprehensively analyzed by gas chromatography–mass spectrometry and two-dimensional gas...     

Synthesis of nitrocyclopropanedicarboxylic acid derivatives by addition of ��-bromonitroalkanes to methylidene malonic, methylidene cyanoacetic or maleic acid derivatives

A potassium carbonate promoted addition of 2-bromonitroalkanes to methylidenemalonic and methylidenecyanoacetic acid derivatives and N-benzylmaleimide leads to the functionalized nitrocyclopropanes. In the case of less active olefins, it is reasonable to use the phase-transfer catalyst Bu₄NPF₆ (10 mol.%), whereas in the case of N-benzylmaleimide, to carry out the process in the ionic liquid [bmim]BF₄.