Co2+/Co+ redox tuning in methyltransferases induced by a conformational change at the axial ligand

Density functional theory and quantum mechanics/molecular mechanics computations predict cob(I)alamin (Co(+)Cbx), a universal B(12) intermediate state, to be a pentacoordinated square pyramidal complex, which is different from the most widely accepted viewpoint of its tetracoordinated square planar geometry. The square pyramidality of Co(+)Cbx is inspired by the fact that a Co(+) ion, which has a dominant d(8) electronic configuration, forms a distinctive Co(+)--H interaction because of the availability of appropriately oriented filled d orbitals. This uniquely H-bonded Co(+)Cbx may have catalytic relevance in the context of thermodynamically uphill Co(2+)/Co(+) reduction that constitutes an essential component in a large variety of methyltransferases.     

Silica gel promoted environment-friendly synthesis of 2,3-disubstituted 4-thiazolidinones

Three-component one pot silica gel promoted synthesis of 2,3-disubstituted 4-thiazolidinones is described. The method provides rapid and easy access to thiazolidinone compounds in good to excellent yields.     

Acetanilide palladacycle: an efficient catalyst for room‐temperature Suzuki–Miyaura cross‐coupling reaction

The catalytic activity of three acetanilide palladacycles derived from easily accessible and commercially available acetanilide derivatives, viz. N‐phenylacetamide ( L1 ), N‐(4‐chlorophenyl)acetamide ( L2 ) and N‐(4‐methylphenyl)acetamide ( L3 ) has been examined in Pd‐catalyzed Suzuki–Miyaura reaction of arylboronic acid with aryl bromides at room temperature. The complex 1L3 exhibited efficient activity in the Suzuki–Miyaura reaction (up to 99% isolated yield) under mild reaction conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Efficient Ring Opening of Aziridines with Carboxylic Acids

An efficient ring cleavage of aziridines with acids has been studied in the absence of any catalyst. The hydrolysis of the products, amino esters, leads to the corresponding amino alcohols. The reaction has been extended to chiral cycloalkyl aziridines, leading to the formation of diastereomers. After separation, these diastereomers have been converted to optically pure amino alcohols in two steps.     

HPLC‐FLD determination of NBD‐cholesterol,its ester and other metabolites in cellular lipid extracts

22‐[N(?7‐Nitrobenz‐2‐oxa‐1,3‐diazol‐4‐yl)amino]‐23,24‐bisnor‐5‐cholen‐3β‐ol (NBD‐cholesterol), a fluorescent cholesterol analog, was an extragenous cholesterol tracer used to study cholesterol absorption and metabolism in cultured cells. In order to measure free intracellular cholesterol and its esters, a precise and sensitive method employing high‐performance liquid chromatography/fluorescence detection (HPLC‐FLD) was developed for the first time. Method validation showed a limit of detection at 30 ng/mL. The calibration curve was linear within the range of 0.0625–10.0 µg/mL (r² = 0.999). Accuracy and precision were highlighted by good recovery and low variations. Apart from NBD‐cholesteryl oleate, two additional cellular metabolites of NBD‐cholesterol, probably an isomer and an oxidation product, were determined in the lipid extracts of Caco‐2 human colon adenocarcinoma cells according to mass spectrometry. In AC29 mouse malignant mesothelioma cells overexpressing acyl‐CoA:cholesterol acyltransferase‐1 (ACAT1) or ACAT2, only the oxidized metabolite was detected. Using the newly developed method, YIC‐C8‐434, a known ACAT inhibitor, was shown to inhibit ACAT activity in Caco‐2 cells, as well as in AC29/ACAT1 or AC29/ACAT2 cells. In conclusion, the sensitive and specific HPLC‐FLD method is a powerful tool for simultaneous quantification of intracellular NBD‐cholesterol and its oleoyl‐ester. Copyright © 2013 John Wiley & Sons, Ltd.     

Tuning of crystal phase structure in hydrated WO3 nanoparticles under wet chemical conditions and studies on their photochromic properties

Hydrated tungsten oxide nanoparticles have been synthesized using a simple wet chemical method while varying the concentration of HCl. XRD studies show that the variation in HCl concentration from 1 M to 6 M in the reaction results into gradual change in crystal structure of hydrated WO₃ from hexagonal (WO₃·0.33H₂O) to pure orthorhombic (WO₃·H₂O), through a series of samples with mixed phase of the two indifferent ratios. The similar variations in the degree of hydration and phase variations have also been observed from Raman, FTIR and TGA studies. The average crystallite size of the hydrated WO₃ particles was estimated to be ～26 nm from XRD line broadening and AFM studies showed the formation of spherical shaped particles for all the samples. The photochromic studies were carried out on the composite films of these materials in the polymeric matrix of polyvinyl alcohol (PVA) while exposing to UV light. The composite films show interesting variations in the photochromic behavior depending on the crystal structure of hydrated WO₃ filler. The photochromic behavior has been explained on the basis of EPR spectra of hydrated WO₃.     

Ecofriendly and facile Nano ZnO catalyzed solvent-free enamination of 1,3-dicarbonyls

Nano zinc oxide (Nano-ZnO) was explored as a reusable catalyst for the enamination of 1,3-dicarbonyls using diverse amines. To make the process environmentally viable, the reaction was carried out under solvent-free conditions and found to give good yield of desired products. The catalyst was characterized by various analytical techniques such as UV-spectroscopy, XRD, and TEM. The catalyst was found to be reusable up to four catalytic cycles without any appreciable loss in activity.