The 5-deoxy-5-methylthio-xylofuranose residue in mycobacterial lipoarabinomannan. absolute stereochemistry, linkage position, conformation, and immunomodulatory activity

Mycobacteria produce a cell-surface glycoconjugate, lipoarabinomannan (LAM), which has been shown to be a potent modulator of the immune response that arises from infection by these organisms. Recently, LAM from the human pathogens Mycobacterium tuberculosis and M. kansasii has been shown to contain an unusual 5-deoxy-5-methylthio-xylofuranose (MTX) residue as well as its corresponding oxidized counterpart, 5-deoxy-5-methylsulfoxy-xylofuranose (MSX). To date, the absolute configuration of these residues and their linkage position to the polysaccharide are unknown, as is their biological role. Through the combined use of chemical synthesis and NMR spectroscopy, we have established that the MTX/MSX residues in these glycoconjugates are of the d-configuration and that they are linked alpha-(1-->4) to a mannopyranose residue in the mannan portion of the glycan. Conformational analysis of the MTX/MSX residue using NMR spectroscopy showed differences in ring conformation and as well as in the rotamer populations about the C-4-C-5 bond, as compared to the parent compound, methyl alpha-d-xylofuranoside. Two of the synthesized disaccharides, 3 and 34, were tested in cytokine induction assays, and neither led to the production of TNF-alpha or IL-12p70. In contrast, both demonstrated modest inhibitory properties when these same cytokines were induced using a preparation of Interferon-gamma and Staphylococcus aureus Cowan strain (SAC/IFN-gamma). These latter observations suggest that this motif may play a role in the immune response arising from mycobacterial infection.     

Isolation of aureol from Smenospongia sp. and cytotoxic activity of some aureol derivatives

The sesquiterpene aureol (1) was isolated by chromatographic fractionation of a non-polar extract from Smenospongia sp. Methylation of aureol yielded 5'-O-methyl-aureol (2) while the prepared acylation products of aureol were 5'-O-acetyl-aureol (3), 5'-O-benzoyl-aureol (4), 5'-O-(4-fluoro-benzoyl)-aureol (5), 5'-O-(4-chlorobenzoyl)-aureol (6), 5'-O-(4-methylbenzoyl)-aureol (7), 5'-O-nicotinoyl-aureol (8), aureol-N,N-dimethylthiocarbamate (9), 5'-O-(2-furoylcarbonyl)-aureol (10), 5'-O-(2-thienoylcarbonyl-aureol (11). The structures of aureol as well as its ten derivatives were established through spectral analysis. The in vitro cytotoxic activities of the eleven compounds were evaluated against Hepa59T/VGH, KB and Hela tumor cell lines.     

On higher-order averaging of time-periodic systems: reconciliation of two averaging techniques

Nonlinear Dynamics - In this paper we show how higher-order averaging can be used to remedy serious technical issues with the direct application of the averaging theorem. While doing so, we...     

Synthesis,characterization, and antimicrobial evaluation of some novel anthracene heterocycles derivatives

A series of novel heterocyclic compounds containing anthracene moiety was synthesized. Reaction of (11R,15S)-9,10-dihydro-9,10-[3,4]furanoanthracene-12,14-dione with 2-cyanoacetohydrazide gave 2-cyano-pyrroloanthracen acetamide (1) , which acts as an adaptable material for the synthesis of new heterocyclic compounds. The synthesized compounds were examined for their antimicrobial activity against Escherichia coli and Staphylococcus aureus via p-iodonitrotetrazolium violet formazon assay. The results exhibited great activity against the tested strains with a minimum bactericidal concentration range from 0.636 to 3.8 mg/mL) and 0.159 to 3.6 mg/mL for E coli and S aureus, respectively. Interestingly, the highest activity was recorded for chromene derivative (6) against both strains.     

Three New Cadinene Derivatives from Xenia Puerto‐Galerae

Chromatographic investigation of an acetone extract of the octocoral Xenia puerto‐galerae afforded three new cadinene sesquiterpenes; 8‐epi‐xenitorin A ( 1 ), 10‐epi‐xenitorin C ( 2 ), and 7‐isopropenyl‐4,10‐dimethyl‐2,3,4,5‐tetrahydronaphthalene ( 3 ), in addition to four known cadinene analogs ( 4 , 11–13 ) and six xenicanes ( 5–10 ). The structures were elucidated through spectroscopic analysis, especially 2D NMR. A biogenetic pathway of 1–3 and analogs was proposed.     

Crystallographic and first-principles density functional theory study on the structure,noncovalent interactions,and chemical reactivity of 1,5-benzodiazepin-2-ones derivatives

The present work arose out of a desire to fundamentally understand the molecular geometry, weak interactions, electron density delocalization, and chemical reactivity features of 1,5-benzodiazepines-containing family. Herein, a complete X-ray crystallographic study, supported by trustworthy sets of computational approaches, has been reported for two organic crystals. Quantifying intramolecular and intermolecular interactions by Hirshfeld-Becke surfaces analysis conjointly with noncovalent interaction-reduced density gradient topological study revealed that supramolecular assemblies are stabilized by N-H ^… O (inter) and O-H ^… N (intra) hydrogen bonds, Cg ^… Cg (π ^… π) and C-H(O) ^… π intercontacts, as well as Van der Waals interactions and steric effects. The long-range-corrected functional wB97XD, which uses Grimme's D2 dispersion model, seems to be just right for our systems. The quantum theory of atoms in molecules analysis confirms that both significant O1-H1…N1 and N2-H2A…O2 H-bonds are weak and electrostatic in nature. Furthermore, global reactivity indices computed via the conceptual density functional theory framework allows these molecules to be classified as moderate electrophiles and marginal nucleophiles. The active sites favorable for nucleophilic/electrophilic attacks were also predicted based on local Parr functions. Finally, a comparative evaluation on the aromaticity character and π-π stacking ability has been done for different (pseudo) rings.     

Metal chelates of Triazine-Schiff-bases: Complex formation of 3-(α-phenyl)ethylidenehydrazino-5,6-diphenyl-1,2,4-triazine with copper(II)

Summary Complex formation of copper(II)-ions with 3-(-Phenyl)ethylidenehydrazino-5,6-diphenyl-1,2,4-triazine (BHT) has been investigated using UV-VIS-, IR-, and electrochemical methods. Optimal pH for the 1:1 complex formation (and therefore for analytical applications) was found at 5.4. This complex could be isolated. The acid dissociation constant of the free ligand ispK _a=13.60; formation constants for 1:1 and 1:2 complexes were found to be logK ₁=12.0 and logK ₂=10.4, respectively. Polarographic reduction of both the free ligand and the Cu(II)-complexes is irreversible, diffusion controlled and like the stability of the complexpH-dependent.In course of absence of the Faculty of Education, Ain Schams University, Roxy, Cairo, Egypt.     

Crystal structure,thermal analysis,and IR spectroscopic investigation of bis(2-amino-6-methyl) pyridinium sulfate

Synthesis, crystal structure refinement, phase transitions studied by thermal analysis, and IR spectroscopic investigation of 2C₆H₉N₂ < eqid2 > ⋅SO₄²⁻ are reported. The title compound crystallizes in the monoclinic space group C2/c (no. 15) with a = 10.5068(4) Å, b = 10.2225(5) Å, c = 14.0422(7) Å, and β = 104.489(3)^∘. A crystal packing diagram shows layers built by all the components of the structure and centered by planes z = 1/4 and 3/4. The pyridine substituents stack forming channels parallel to the c direction with dimensions of 4.163(1) Å and 5.148(4) Å. Thermal analysis shows that the anhydrous compound possesses an irreversible weak phase transition.