Nucleophilic behaviour of DBU towards imidazolides: one-pot synthesis of ε-caprolactam derived carbamates and amides

Herein, we report the DBU ring opening reactions with imidazolide which can be a facile method to generate the library of ε-caprolactam derived carbamates and amides under one-pot condition.     

Studies in claisen rearrangement : Novel thermal transformation of α-aryloxymethylacrylic acids and their derivatives

α-Aryloxymethylacrylic acids and their derivatives have been found to undergo some novel thermal transformations leading to the formation of ‘ene’ dimers. The structure of the dimer has been revised on the basis of degradation studies, extensive spectral data and isolation of intermediates.     

Trifluoroacetic acid catalyzed and thermal rearrangement ofα- aryloxymethyl cinnamic acids.

Severalα- aryloxymethyl cinnamic acids $\text{1}$ have been rearranged in refluxing trifluoroacetic acid (TFA). The thermal rearrangement of the same acids in Polyethylene glycol - 200 (PEG - 200) has also been investigated.     

A dianionic oxy-cope rearrangement route to benzotropones - part XII

The divinyl carbinols $\text{3}$ and $\text{6}$ furnished the benzotropones $\text{4}$ and $\text{7}$ respectively, when treated with base.     

Nanocrystalline metal oxides as destructive adsorbents for organophosphorus compounds at ambient temperatures

Nanocrystals of magnesium oxide react with organophosphorus compounds at room temperature by dissociative chemisorption, which we term "destructive adsorption". This process involves cleavage of P-O and P-F bonds (but not P-C bonds) and immobilization of the resultant molecular fragments. These ultrafine powders have unusual crystalline shapes and possess high surface concentrations of reactive edge/corner and defect sites, and thereby display higher surface reactivity, normalized for surface area, than typical polycrystalline material. This high surface reactivity coupled with high surface area allows their use for effective decontamination of chemical warfare agents and related toxic substances. Herein data is presented for paraoxon, diisopropylfluorophosphate (DFP), and (CH3CH2O)2P(O)CH2-SC6H5 (DEPTMP). Solid-state NMR and IR spectroscopy indicate that all OR and F groups dissociate; this leaves bound -PO4, -F, and -OR groups for paraoxon, DFP, and DEPTMP, respectively. For paraoxon, it was shown that one monolayer reacts. For DEPTMP, the OR groups dissociate, but not the P-CH2SC6H5 group. The nanocrystalline MgO reacts much faster and in higher capacity than typical activated carbon samples, which physisorb but do not destructively adsorb these phosphorous compounds.     

A simple method for the determination of benzo[a]pyrene and benzo[k]fluoranthene in a mixture

Atmospheric particulate matter is routinely analysed for the concentration of the carcinogen benzo[a]pyrene (BaP). Benzo[k]fluoranthene (BkF) has identical spectral characteristics and interferes in the fluorimetric estimation. A simple method for the determination of BaP in the presence of BkF is described. Based on quenching of the fluorescence of BaP by the addition of small amounts of nitromethane, the method can be used for accurate estimation for wide concentration ratios of BaP to BkF ranging from 0.1 to 10.0.     

Coordination chemistry at the molybdenum site of sulfite oxidase: redox-induced structural changes in the cysteine 207 to serine mutant

The redox chemistry of the molybdenum site of the C207S mutant of recombinant human sulfite oxidase has been studied via potentiometric titrations employing both electron paramagnetic resonance (EPR) spectroscopy and X-ray absorption spectroscopy (XAS) as probes of the active site structure. In earlier EXAFS studies, oxidized Cys207Ser enzyme has been shown to possess a novel tri-oxo active site, in which Ser207 does not appear to be a ligand to Mo [George, G. N.; Garrett, R. M.; Prince, R. C.; Rajagopalan, K. V. J. Am. Chem. Soc. 1996, 118, 8588-8592]. Redox titrations show that the active site is modified under reducing conditions to a mono-oxo Mo(IV) species, probably with Ser207 ligated to the metal. The Mo(IV) species can be reoxidized to a mono-oxo Mo(V) species still coordinated to Ser207, which in turn can be further reoxidized to yield the initial tri-oxo Mo(VI) structure with loss of Ser207 ligation.     

Mixing Properties of Two-Dimensional Lattice Solutions of Amphiphiles

Lattice Monte Carlo simulations of two-dimensional amphiphile solutions are used to examine the accuracy of the mixing properties predicted by lattice theories such as the Flory-Huggins theory, random-solution approximation, and quasichemical approximation. The internal energy, Helmholtz free energy, and entropy of mixing have been calculated from the configurational energy data obtained from the simulations, and the effect of nonrandom mixing on these properties has been determined. The quasichemical approximation predicts the entropy and Helmholtz free energy of mixing accurately for the amphiphile solution, but fails to predict the energy of mixing, due to the presence of microphase (self-aggregation) separation, which is beyond the reach of the quasichemical approximation, a mean-field theory. Helmholtz free energy of mixing is predicted accurately, and the shielding of the solvophobic segments in the microphase leads to small energies of mixing compared to the entropy of mixing. Copyright 2000 Academic Press.     

Quantitative determination of ragaglitazar in rat plasma by HPLC: validation and application in pharmacokinetic study

A specific, accurate, precise and reproducible high-performance liquid chromatography (HPLC) method was developed for the estimation of ragaglitazar [(-) DRF 2725, NNC 61-0029], a novel anti-diabetic agent, in rat plasma. The assay procedure involved simple liquid/liquid extraction of ragaglitazar and internal standard (IS, troglitazone) from plasma into ethyl acetate. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected onto a Kromasil KR 100 - 5C(18) column (4.6 x 250 mm, 5 micro m). Mobile phase consisting of 0.01 M potassium dihydorgen ortho phosphate (pH 3.2) and acetonitrile (30:70, v/v) was used at a flow rate of 1.0 mL/min. The eluate was monitored using an UV detector set at 240 nm. Ratio of peak area of analyte to IS was used for quantification of plasma samples. Nominal retention times of IS and ragaglitazar were 6.9 and 12.2 min, respectively. The standard curve for ragaglitazar was linear (r(2) > 0.999) in the concentration range 0.2-100 micro g/mL. Absolute recovery was >87% from rat plasma for both analyte and IS. The lower limit of quantification (LLOQ) of ragaglitazar was 0.2 micro g/mL. The inter- and intra-day precision in the measurement of quality control (QC) samples, 0.2, 1.0, 5.0 and 50 micro g/mL, were in the range 1.32-3.70% relative standard deviation (RSD) and 1.19-9.39% RSD, respectively. Accuracy in the measurement of QC samples was in the range 94.28-107.45%. Analyte and IS were stable in the battery of stability studies, viz. benchtop, autosampler and freeze/thaw cycles. Stability of ragaglitazar was established for 1 month at -20 degrees C. The application of the assay to a pharmacokinetic study in rats is described.