Brönsted acid hydrotrope combined catalyst for environmentally benign synthesis of quinoxalines and pyrido[2,3-b]pyrazines in aqueous medium

A new Brönsted acid hydrotrope combined catalyst (BAHC) has been developed and applied in acid catalyzed synthesis of pyrido[2,3-b]pyrazines and quinoxalines in an aqueous medium at ambient temperature with excellent yields. Interestingly, the catalyst can be easily recovered after the reactions and reused. Furthermore, BAHC catalyst worked well and avoids the use of organic solvents. We have reported herein the synthetic pathway which has less disastrous effect in the atmosphere and human survival.     

Antituberculosis agent diaportheone B: synthesis, absolute configuration assignment, and anti-TB activity of its analogues

First synthesis of diaportheone B, an antituberculosis agent isolated from endophytic fungus Diaporthe sp. P133 is reported using two complementary routes, a one step and a three-step sequence. The absolute configuration of diaportheone B was determined by using X-ray crystal structure analysis of its dibromo derivative. In addition, we have prepared several close analogues of diaportheone B and determined their anti-TB potential using Alamar-blue assay (H(37)Rv).     

Purification and Partial Characterization of Lignin Peroxidase from <Emphasis Type="Italic">Acinetobacter calcoaceticus</Emphasis> NCIM 2890 and Its Application in Decolorization of Textile Dyes

Lignin peroxidase was purified (72-fold) from Acinetobacter calcoaceticus NCIM 2890. The purified lignin peroxidase (55–65 kDa) showed dimeric nature. The maximum enzyme activity was observed at pH 1.0, between a broad temperature range of 50 and 70°C, at H₂O₂ concentration (40 mM) and the substrate concentration (n-propanol, 100 mM). Purified lignin peroxidase was able to oxidize a variety of substrates including Mn²⁺, tryptophan, mimosine, l-Dopa, hydroquinone, xylidine, n-propanol, veratryl alcohol, and ten textile dyes of various groups indicating as a versatile peroxidase. Most of the dyes decolorized up to 90%. Tryptophan stabilizes the lignin peroxidase activity during decolorization of dyes.     

Antioxidant activities of Swertia decussata xanthones

The lipid peroxidation inhibitory activities of four hydroxyxanthones, isolated from the whole plant Swertia decussata, were evaluated for the first time. The most promising antioxidant among the xanthones, 1,7,8-trihydroxy-3-methoxyxanthone (swertianine, 4) was also tested for its scavenging potential against DPPH and superoxide radicals. The data clearly revealed good antioxidant activity of the xanthones, especially 4 which also showed strong protection against y-ray induced pBR322 DNA damage. A comparison of the radioprotecting activities of the monomethylated tetrahydroxyxanthone 4 with that of its congener, 1,3,7-trihydroxy-8-methoxyxanthone (5) revealed that the radioprotecting activity was not affected by the position of methylation.     

Cadmium(II) binding by soil-derived fulvic acid measured by anodic stripping voltammetry

Titrations of aqueous solutions of soil fulvic acid (30, 45, and 60 mg l^-1) with cadmium ion solutions at pH 6 and 7 reveal unusual shapes in the stripping current (i_s) vs. total cadmium ion (C_cd²⁺) curves. The expected inflections occur in the titration curves at 8–16 μM. at pH 6 and 12–26 μM at pH 7. In addition, there is an initial rapid increase in i_s at very low C_cd²⁺. The initial rapid increase in current is attributed to labile cadmium—fulvic acid complexes that contribute to i_s by rapid dissociation. Subsequent addition of cadmium ion results in moderately labile complexes and i_s becomes partially kinetically controlled. The stripping current was corrected for kinetic current contributions from dissociation of complexes, and total ligand concentrations, conditional stability constants, and upper slopes were calculated from data well past the titration end-point. The use of upper slopes after kinetic current corrections as in situ calibration curves, allowed calculations of equilibrium cadmium concentrations. The data show that both kinetic current corrections and in situ calibration curves are necessary to avoid substantial errors in calculations of equilibrium cadmium concentrations from anodic stripping voltammetric experiments.     

Sustainable synthesis of sulfonamides using supported ionic liquid phase catalyst containing Keggin‐type anion

A silica‐supported ionic liquid phase catalyst containing Keggin‐type anion has been prepared by covalent grafting of ferrocene‐tagged ionic liquid in a matrix of silica followed by anion metathesis reaction. This novel catalyst served as a robust heterogeneous catalyst for the synthesis of biologically active sulfonamides from 4‐toluenesulfonyl chloride and amines. Additionally, recycling experiments showed that the catalyst could be reused five times. Copyright © 2015 John Wiley & Sons, Ltd.     

Green synthesis of quinolines via A3-coupling by using graphene oxide-supported Brønsted acidic ionic liquid

Research on Chemical Intermediates - Graphene oxide-supported Bronsted acidic ionic liquid ([GrBenzImi]SO3H) has been prepared by covalent grafting of benzimidazole unit in the matrix of graphene...     

Spectrophotometric determination of Fe(III) by using casein-functionalized gold nanoparticles

The preparation and application of casein-capped gold nanoparticles (AuNPs) as a specific probe for ferric ions Fe(III) is reported. The functionalized AuNPs exhibit narrow size distribution and form stable dispersions in water of different ionic strengths and basicity. The presence of diverse functional groups from the side chain of peptides warrants colloidal stability of AuNPs and also assists recognition of Fe(III) in versatile conditions. Fe(III) ion reportedly causes the aggregation of AuNPs and a red-shift in absorbance toward longer wavelength (660 nm). A spectrophotometric method is appropriate for selective detection of Fe(III) and the spectral shift is also accompanied by a color change from red to blue. The aggregation of AuNPs is not suppressed after the addition of NaOH or at moderate ionic strength. The resulting spectrophotometric method works for Fe(III) in the concentration range of 0.1 to 0.9 μM and has a detection limit of 450 nM. The AuNP probe can also detect Fe(III) ion content in real samples at the same detection limit, which is much lower than the maximum contaminant level allowed for Fe(III) in drinking water (5.37 μM) by the U.S. Environmental Protection Agency.

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Graphical abstract Casein peptide functionalized gold nanoparticles: synthesis, characterization, and their application to the visual detection of Fe(III).

     

Thiazolidinediones as a Novel Class of Algicides Against Red Tide Harmful Algal Species

This paper reports the synthesis of 28 thiazolidinedione derivatives along with their algicidal activity against microalgae causing harmful algal blooming. Among the 28 compounds tested, most showed effective algicidal activity against Heterosigma akashiwo, Chattonella marina, and Cochlodinium polykrikoides, while non-harmful algae were relatively tolerant to these thiazolidinedione derivatives. Compounds 6, 13, and 22 were the most potent against C. polykrikoides with IC₅₀ values <0.5 μM. Among the thiazolidinedione derivatives tested, compounds 7, 13, 27, and 28 were extremely competent and selective to C. polykrikoides with IC₅₀ values ranging from 0.1 to 2 μM, while C. marina and H. akashiwo showed an IC₅₀ value ranging from 30 to 130 μM. These results show that some thiazolidinedione derivatives can act as potent algicides against harmful algal blooms.     

Short and Efficient Synthesis of Oxazinone- and Thiazinone-Containing Bicyclic Heteroaromatic Aldehydes

Short and efficient route for the synthesis of oxazinone- and thiazinone-containing bicyclic heteroaromatic aldehydes, which involves the key step of palladium-catalyzed reductive carbonylation, is described. Overall routes for the synthesis of these aldehydes are short, versatile, and scalable with good yields of the product.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]