Unprecedented ‘ring transformation-rearrangement’ of pyran-2-ones into 5,6-dihydropyran-2-ones through insertion of acetol

One-pot efficient synthesis of functionalized 5,6-dihydropyran-2-ones has been delineated by reacting 2H-pyran-2-ones and acetol in the presence of a base at room temperature. The formation of 5,6-dihydropyran-2-ones revealed that the reaction proceeded in a unique ‘ring transformation-rearrangement’ sequence.     

Pentavalent Arsenate Reductase Activity in Cytosolic Fractions of <Emphasis Type="Italic">Pseudomonas</Emphasis> sp., Isolated from Arsenic-Contaminated Sites of Tezpur,Assam

Pentavalent arsenate reductase activity was localized and characterized in vitro in the cytosolic fraction of a newly isolated bacterial strain from arsenic-contaminated sites. The bacterium was gram negative, rod-shaped, nonmotile, non-spore-forming, and noncapsulated, and the strain was identified as Pseudomonas sp. DRBS1 following biochemical and molecular approaches. The strain Pseudomonas sp. DRBS1 exhibited enzymatic machinery for reduction of arsenate(V) to arsenite(III). The suspended culture of the bacterium reduced more than 97% of As(V) (40–100 mM) to As(III) in 48 h. The growth rate and total cellular yield decreased in the presence of higher concentration of arsenate. The suspended culture repeatedly reduced 10 mM As(V) within 5 h up to five consecutive inputs. The cell-free extracts reduced 86% of 100 μM As(V) in 40 min. The specific activity of arsenate reductase enzyme in the presence of 100 μM arsenate is 6.68 μmol/min per milligram protein. The arsenate reductase activity is maximum at 30 °C and at pH 5.2. The arsenate reductase activity increased in the presence of electron donors like citrate, glucose, and galactose and metal ions like Cd⁺², Cu⁺², Ca⁺², and Fe⁺². Selenate as an electron donor also supports the growth of strain DRBS1 and significantly increased the arsenate reduction.     

High pressure studies on the electrical resistivity of As–Te–bond Si glasses and the effect of network topological thresholds

The variation of resistivity in an amorphous As₃₀Te_70?x Si _x system of glasses with high pressure has been studied for pressures up to 8 GPa. It is found that the electrical resistivity and the conduction activation energy decrease continuously with increase in pressure, and samples become metallic in the pressure range 1.0–2.0 GPa. Temperature variation studies carried out at a pressure of 0.92 GPa show that the activation energies lie in the range 0.16–0.18 eV. Studies on the composition/average co-ordination number ? r? dependence of normalized electrical resistivity at different pressures indicate that rigidity percolation is extended, the onset of the intermediate phase is around ? r?=2.44, and completion at ? r?=2.56, respectively, while the chemical threshold is at ? r?=2.67. These results compare favorably with those obtained from electrical switching and differential scanning calorimetric studies.     

An Expeditious Study of the Nature of Halogen(S) at γ-Positions in Carbonyl Compounds

The detailed study, of the behaviour of di/tri halo carbonyls to act as the synthetic equivalents of corresponding mono γ-halo carbonyls, is carried out.     

Isolation and HPTLC Analysis of Iridoids in Premna integrifolia,an Important Ingredient of Ayurvedic Drug Dashmool

JPC – Journal of Planar Chromatography – Modern TLC - Premna integrifolia is an important constituent of the famous herbal formulation “Dashmool” of the Indian Ayurvedic...     

Insights into Associating Fluid Properties and Microstructure from Classical Density Functional Theory

Self-assembly, important in industrial and biological processes, is governed not only by molecular size and shape, but also by hydrogen bonding forces and hydrophobicities, both of which have important temperature-dependent consequences. Recent advances in statistical mechanics enable the study of these processes at the molecular level. We discuss one such approach based on classical density functional theory. The theory, based on extensions and simplifications of Wertheim’s theory for associating molecules, is applicable to study the behavior of water at hydrophobic and hydrophilic surfaces and supramolecular assembly based on intermolecular association of polyatomic molecules. Insights into the theory and into the physics of associating molecules are discussed.     

An expeditious protocol for sesquiterpene-cored functionalized arenes from S-(−)-citronellal

An expeditious straightforward synthesis of sesquiterpene-cored arenes functionalized with electron-withdrawing or electron-donating substituents is described and illustrated by Michael addition of S-(−)-citronellal on functionalized 2H-pyran-2-one in a single step at room temperature. The reaction was further generalized by synthesizing isoprenylated 9,10-dihydrophenanthrene-2-carbonitrile using 5,6-dihydro-2-oxo-4-sec-amino-2H-benzo[h]chromene-3-carbonitriles and S-(−)-citronellal under similar reaction conditions.     

A vicarious synthesis of unsymmetrical meta- and para- terphenyls from 2H-pyran-2-ones

An innovative synthesis of terphenyls functionalized with electron-withdrawing or -donating substituents is described and illustrated by carbanion-induced ring transformation of 2H-pyran-2-ones with 2-methoxyacetophenone in excellent yields. The existing protocols for the synthesis of terphenyls are generally inter- and intramolecular aryl-aryl cross couplings in the presence of metal complexes. In this letter, we report a potentially useful alternative to conventional metal-catalyzed cross-coupling reactions.     

Synthesis and carboxylate anion binding studies on cyclic sugar-amino acid hybrids

Abstract

Here in, the condensation of boc-glycine with 2,6-anhydro-3,4,5-tri-O-benzyl-D-gluco-heptitol followed by its boc-deprotection to form 2,6-anhydro-3,4,5-tri-O-benzyl-D-gluco-heptitolyl bis-glycinate, which in turn on condensation with succinic acid/pyridine-2,6-dicarboxylic acid led to the formation of sugar-amino acid hybrid macrocyclic compounds 4, 6 and debenzylated marocyclic compound 5, having amide bonds that function as efficient host for polar, hydrogen bond acceptors and carboxylate ions. The anion inclusion capability of synthesized macrocylic hosts has been evaluated by the study of their binding with boc-GlyCOOˉ anion as guest through 1H NMR titration studies in CDCl₃. The binding constant (K_a) of boc-GlyCOOˉ guest with macrocyclic hosts 4 and 6 involving succinate and pyridine-2,6-dicarboxylate linkers was found to be 9.201?×?10³ and 1.437?×?10⁴ M^?1, respectively. The higher binding constant was observed in the complex of boc-GlyCOOˉ with pyridine-dicarboxylate containing host may be due to the extra rigidity & suitable conformation attained by the presence of rigid-aromatic dicarboxylate linker.