Mass spectral study of meso-alkyl and meso-cycloalkyl calix(4)pyrroles under electron impact conditions

A series of meso-cycloalkyl calix(4)pyrroles (I) and meso-dialkyl calix(4)pyrroles (II) has been studied under electron ionization (EI) mass spectral conditions. All the calix(4)pyrroles showed prominent molecular ions. The cleavage of the C--C bond linked at position 2 of the pyrrole ring (beta-cleavage) is the foremost and dominant fragmentation process. The beta-cleavage process, either through ring opening or directly, results in the loss of an alkyl radical from the molecular ion. The collision-induced dissociation (CID) spectra of I showed specific sequential expulsion of pyrrole and/or cycloalkyl rings from the molecular ion with or without hydrogen migrations, revealing more information on the structure of individual compounds than was available from the EI spectra. The isomeric cycloalkyl calix(4)pyrroles showed distinguishable CID spectra, indicating structure specificity in initial ring opening whereas, in the case of II, the EI mass spectrum contains all the structure-indicative fragment ions. The CID spectra of II resulted in a dominant [M-R]+ ion, with other characteristic ions being less abundant.     

Formation of a stable 14-helix in short oligomers of furanoid cis-beta-sugar-amino acid

Oligomers of a new class of sugar amino acids (SAA) using a xylofuranoic acid has been shown to generate a robust 14-helix. The design involved the use of xylofuranose with a cis arrangement between the amine and carboxyl groups to promote the adoption of a 14-helix instead of a mixed 12/10-helix observed in a sugar oligomer using a ribofuranoic acid and beta-Ala. The observation of a stable right-handed 14-helix in a cis-SAA is unprecedented.     

Electrospray ionisation tandem mass spectrometric study of hydrogen-bonding interactions of some disaccharides with lysine

The efficiency of formation of protonated heterotrimers of lysine with underivatised sugars (mono-, di-, and trisaccharides) and N-acetylglucosamine (N-AcGlc) was studied under electrospray ionisation conditions. The collision induced dissociation spectra of [Lys + sugar + NAcGlc + H](+) resulted in [Lys + NAcGlc + H](+) and [Lys + sugar + H](+) as the major product ions. Relative abundances of these two fragments reflect the extent of adduct formation of protonated lysine plus sugar, with reference to the reference compound NAcGlc. This relative abundance ratio was found to be characteristic of the sugar structure. In this way it was observed that the ability of lysine to form a protonated heterodimer with neutral sugars increases with an increase in the number of acetal oxygens. Lactose showed an anomalously high affinity for protonated Lys, possibly reflecting the axial hydroxyl at C4. The postulated involvement of the epsilon-NH(2) group of lysine in the formation of protonated heterodimers with sugars was supported by similar results of similar experiments with NH(3) in place of lysine.     

Trace level detection and identification of chemicals related to the chemical weapons convention from complex organic samples

A solid-phase extraction (SPE) method involving selective usage of solvents has been developed for trace level identification of chemical warfare agents (CWAs) present in a complex organic background. The total ion chromatograms obtained from direct gas chromatography-electron ionization mass spectrometric analysis of samples spiked with CWAs in the presence of diesel are very complex and dominated by hydrocarbon peaks and the same after treatment with SPE show distinct peaks corresponding to spiked chemicals. The recovery of samples from SPE is found to be 70-85% at the 10 ppm level.     

Rotational isomerism between the E and Z forms of o-substituted benzo-N-methyl hydroxamic acids in strong acid

The $\text{E}$∠$\text{Z}$ equilibrium of the cations of benzo hydroxamic acids, in mineral acid, was studied utilizing ¹H NMR spectroscopy, NOEDS and MNDO claculations     

Three new ingol diterpenes from Euphorbia nivulia: evaluation of cytotoxic activity

The latex of Euphorbia nivulia afforded three new ingol diterpenes, 3-acetyl-8-methoxyl-7-angolyl-12-hydroxylingol (7), 3,12-diacetyl-7-hydroxy-8-methoxylingol (8), and 3,12-diacetyl-7-angolyl-8-hydroxylingol (9) along with five known ingol diterpenes 2-6 and a known triterpene cyclonivulinol (1). Their structures were established by means of spectroscopic analysis. Diterpenes 2-9 were evaluated for their cytotoxic activity.     

Influence of substrate nature on the growth of copper oxide thin films

Cu thin films were deposited on Si(111), glass, and quartz substrates by magnetron sputtering. X‐ray diffraction, SEM, and photoemission electron microscope studies were carried out to characterize the films. An influence of the nature of substrate on the Cu₂O and CuO phases formed was observed. Copper silicide formation in case of silicon substrates aided in formation of Cu₂O rather than CuO unlike glass and quartz substrates. Formation of nanocrystallites was observed by SEM and X‐ray diffraction. Copyright © 2016 John Wiley & Sons, Ltd.     

Chitosan-iron oxide nanocomposite based electrochemical aptasensor for determination of malathion

An electrochemical aptasensor based on chitosan-iron oxide nanocomposite (CHIT-IO) film deposited on fluorine tin Oxide (FTO) was developed for the detection of malathion. Iron oxide nanoparticles were prepared by co-precipitation method and characterized by Transmission electron microscopy and UV–Visible spectroscopy. The biotinylated DNA aptamer sequence specific to the malathion was immobilized onto the iron oxide doped-chitosan/FTO electrode by using streptavidin as linking molecule. Various characterization studies like Field Emission-Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Electrochemical studies were performed to attest the successful fabrication of bioelectrodes. Experimental parameters like aptamer concentration, response time, stability of electrode and reusability studies were optimized. Aptamer immobilized chitosan-iron oxide nanocomposite (APT/SA/CHIT-IO/FTO) bioelectrodes exhibited LOD of about 0.001 ng/mL within 15 min and spike-in studies revealed about 80–92% recovery of malathion from the lettuce leaves and soil sample.     

Biological potential of pyrimidine derivatives in a new era

Pyrimidine and its derivatives play a wide role in drug discovery processes and have considerable chemical significance and biological activities. Pyrimidines are the building blocks of many natural compounds such as vitamins, liposacharides, and antibiotics. Pyrimidine is used as parent substance for the synthesis of a wide variety of heterocyclic compounds and raw material for drug synthesis and is also crucial in the theoretical development of heterocyclic chemistry and in organic synthesis. Pyrimidine derivatives are vital in several biological activities, i.e. antihypertensive, anticancer, antimicrobial, anti-inflammatory, and antioxidant activity. This creates interest among researchers who have synthesized a variety of pyrimidine derivatives.     

Green synthesis and antibacterial evaluation of some new 1-aryl-3-(1-aryl-1<Emphasis Type="Italic">H</Emphasis>-[1,2,3]triazol-4-yl)-propenones

A new series of 1-aryl-3-(1-aryl-1H-[1,2,3]triazol-4-yl)propenones (6a–6j) was synthesized by condensation of substituted acetophenones (5a–5c) with substituted 1-aryl-1H-[1,2,3]triazole-4-carbaldehydes (4a–4d) in the presence of potassium hydroxide under conditions of grinding and microwave irradiation. All the newly synthesized compounds were characterized by the IR, NMR, and mass spectroscopic analyses and their antibacterial activity against gram-positive and gram-negative bacterial strains was evaluated. Among the compounds synthesized, better activity was exhibited by 6a, 6c, 6f, 6g, and 6i.