Conformations of cycloundecane

Cycloundecane (1) was shown to exist at -183.1 degrees C as a mixture of the [12323] (approximately 59%) and [335] (approximately 41%) conformations. Populations were determined from the (13)C NMR spectrum, and assignments were based on the (13)C spectra, calculated free energies and chemical shifts, and information from the literature, including X-ray studies of solid derivatives and calculated barriers.     

Density and viscosity studies of symmetrical tetra-n-alkylammonium bromides in water-ethanol mixtures at 303.15 K1

The densities and viscosities of tetra-n-alkylammonium bromides, R₄NBr (R=CH₃ to C₄H₉), NaBPh₄ and NaBr have been measured in 0, 10, 30, 50, 70, 90, and 100 wt % ethanol + water at 303.15 K. From the densities, apparent and limiting partial molar volumes of the electrolytes and ions in these mixture have been evaluated. The viscosity data have been analyzed with the help of Jones-Dole equation and the viscosity B-coefficients have been determined. The viscosity B-coefficients are further split up in to their ionic contributions.     

Synthesis and Antibacterial Activity of Some 3,5‐Diphenyl and 1,3,5‐Triphenyl‐2‐pyrazolines

Some new 3,5‐diphenyl and 1,3,5‐triphenyl‐2‐pyrazolines derivatives were synthesized by reacting 1,3‐diphenyl‐2‐propen‐1‐ones with hydrazine hydrates and phenyl hydrazine in ethanol. The structural elucidation of the compounds was performed by IR, ¹H NMR and elemental analysis. All examined compounds showed appreciable antibacterial activity.     

Design and synthesis of novel type VI-like β-turn mimetics. Diversity at the i+1 and the i+2 position

In this paper, a synthetic approach for functionalised 5-aminopiperidinone-2-carboxylate (APC) systems as non-pro cis-peptide bond containing external β-turn mimics is presented. The scope and limitations of the synthetic method are discussed and the potential turn inducing properties of a model compound are evaluated by means of molecular modelling and NMR analysis.     

A Novel Strategy for 2,6-Dideoxy-L-Hexoses: An Application to 3-Amino-2,3,6-Trideoxy-L-Lyxo-Hexopyranose (L-Daunosamine)

Abstract

A synthetic strategy wherein C-l/6 of D-glucose are transformed into C-6/1 of L-daunosamine, circumventing the critical step of epimerisation of the C-5 center is described.     

Determination of the appetite suppressant P57 in Hoodia gordonii plant extracts and dietary supplements by liquid chromatography/electrospray ionization mass spectrometry (LC-MSD-TOF) and LC-UV methods

Hoodia gordonii is traditionally used in South Africa for its appetite suppressant properties. P57AS3 (P57), an oxypregnane steroidal glycoside, is the only reported active constituent from this plant as an appetite suppressant. Effective quality control of these extracts or products requires rapid methods to determine P57 content. New methods of liquid chromatography/mass spectrometry (LC/MS) and LC-UV for analysis of P57 from H. gordonii have been developed. The quantitative determination of P57 was achieved with a Phenomenex Gemini (Torrance, CA) reversed-phase column using gradient mobile phase of water and acetonitrile, both containing 0.1% acetic acid. The method was validated for linearity, repeatability, and limits of detection and quantification. Good results were obtained in terms of repeatability (relative standard deviation <5.0%) and recovery (98.5-103.5%). The developed methods were applied to the determination of P57 for H. gordonii plant samples, one related genus (Opuntia ficus-indica), and dietary supplements that claim to contain H. gordonii.     

Evaluation of Probiotic Characteristics of Siderophoregenic <Emphasis Type="Italic">Bacillus</Emphasis> spp. Isolated from Dairy Waste

Siderophoregenic Bacillus strain DET9 has been selectively isolated from dairy waste. It was evaluated for probiotic characteristics and susceptibility pattern against antibiotics. Its spores showed excellent tolerance to simulated gastrointestinal tract conditions and exhibited antimicrobial activity against organisms such as Escherichia coli, Micrococcus flavus, and Staphylococcus aureus. Its susceptibility to antibiotics reduces the prospect to donate resistance determinants if administered in the form of probiotic preparations. It was observed to produce ∼60 mg/l catecholate type of siderophore under iron stressed conditions, identified as a 2,3-dihydroxy benzoic acid by high-performance liquid chromatography, infrared spectroscopy, nuclear magnetic resonance, and mass spectral analysis. Partial 16S-rRNA gene sequencing analysis shows that the isolate exhibited homology with Bacillus thuringiensis and Bacillus weihenstephanensis, whereas biochemical characterization revealed its novelty. DET9 exhibited no mortality of fishes in a 60-day trial, when fishes (surfi tetra) were challenged up to 100 ppm cell concentration, with their daily diet.     

Synthesis,Spectroscopic Characterization,and In Vitro Antimicrobial Potency of Sulfur-Bonded Complexes of Boron(III)

The present article describes the synthesis and characterization of tetracoordinated boron (III) complexes with monobasic bidentate ligands (L ¹ H, L ² H, L ³ H, L ⁴ H, L ⁵ H, and L ⁶ H) having the general formulae PhB(L)(OH) and PhB(L) ₂ . The 1:1 and 1:2 reactions of phenyl boronic acid with monobasic bidentate ligands resulted in the formation of colored solids. The complexes have been characterized by elemental analysis, molecular weight determinations, and IR and NMR ( ¹ H, ¹³ C and ¹¹ B) spectroscopy, as well as UV-vis spectral studies. Based on these studies, a tetrahedral geometry has been proposed for the resulting complexes. The ligands, along with their complexes, have been screened in vitro against a number of pathogenic fungal and bacterial strains. The studies indicate that the boron chelates are more potent than the parent ligands.     

Synthesis of highly functionalized 2(1H)-pyrazinone 3-carboxamide scaffolds

Synthesis of highly functionalized 2(1H)-pyrazinone 3-carboxamide derivatives is reported. A one-pot, two-step process including the base-mediated reaction of N,N-disubstituted aminoacetonitrile derivatives 18 with 3,5-dihalo-2(1H)-pyrazinones 1 afforded substituted aminoacetonitrile pyrazinone derivative 19, which on subsequent oxidation followed by transamidation of the resulting intermediate with primary or secondary amines gave the corresponding highly functionalized 2(1H)-pyrazinone 3-carboxamide derivatives 21.