Comparison of arylboron-based nucleophiles in Ni-catalyzed Suzuki-Miyaura cross-coupling with aryl mesylates and sulfamates

The efficiency of arylboron-based nucleophiles, boronic acid, potassium trifluoroborate, neopentylglycolboronate, and pinacol boronate in nickel-catalyzed Suzuki-Miyaura cross-coupling reactions with the two C-O electrophiles, mesylates, and sulfamates was compared. Arylboronic acid is the most reactive and most atom-economic of the four boron species studied. Arylpotassium trifluoroborate cross-couples efficiently only in the presence of water. In the absence of water, aryl neopentylglycolboronate is more efficient, less expensive, and more atom-economic than aryl pinacolboronate.     

<Emphasis Type="Italic">Bacillus</Emphasis> spp. of Human Origin: A Potential Siderophoregenic Probiotic Bacteria

Bacillus spp. ST13, isolated from human stool, was evaluated for siderophoregenic and probiotic qualities prior to its possible application for iron nutrition in humans and animals. It was tested for siderophore production in iron-limiting conditions and found to produce catecholate type of siderophore on the basis of high-performance liquid chromatography (HPLC), FT-IR, NMR, and mass spectra analysis. The isolate was screened for probiotic properties as per WHO and FAO guidelines. The strain ST13 can survive stomach acidity, bile salt and partially simulated gastrointestinal tract conditions. It was susceptible to most of the antibiotic tested and showed antimicrobial activity against enteric pathogens like Salmonella typhimurium, Streptococcus pyogenes, and Staphylococcus aureus. Strain ST13 showed close similarity with Bacillus subtilis using 16S r-RNA gene sequence analysis and biochemical characterization. The methanolic extract of ST13 siderophore was evaluated for DPPH radical scavenging activity, which showed 94.55 ± 0.9% of radical scavenging effect.     

Synthesis of meso‐Pyrrole‐Substituted 22‐Oxacorroles by a “3+2” Approach

Unsymmetrical 22‐oxacorrole containing two aryl groups and one pyrrole group at the meso position was synthesized by condensing one equivalent of 16‐oxatripyrrane with one equivalent of meso aryl dipyromethane under mild acid‐catalyzed conditions followed by oxidation with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ). This [3+2] condensation approach was expected to yield meso‐free 25‐oxasmaragdyrin but unexpectedly afforded unsymmetrical meso‐pyrrole‐substituted 22‐oxacorrole. We demonstrated the versatility of the reaction by synthesizing four new meso‐pyrrole‐substituted 22‐oxacorroles. The reactivity of α‐position of meso‐pyrrole was tested by carrying out various functionalization reactions such as bromination, formylation, and nitration and obtained the functionalized meso‐pyrrole‐substituted 22‐oxacorroles in decent yields. The X‐ray structure obtained for one of the functionalized meso‐pyrrole substituted 22‐oxacorrole revealed that the macrocycle was nearly planar and the meso‐pyrrole was in the perpendicular orientation with respect to the macrocyclic plane. The meso‐pyrrole‐substituted 22‐oxacorroles absorb strongly in 400–700 nm region with one strong Soret band and four weak Q bands. The 22‐oxacorroles are strongly fluorescent and showed emission maxima at ≈650 nm with decent quantum yields and singlet‐state lifetimes. The 22‐oxacorroles are redox‐active and exhibited three irreversible oxidations and one or two reversible reduction(s). A preliminary biological study indicated that meso‐pyrrole corroles are biocompatible.     

The complexity of approximating a nonlinear program

We consider the problem of finding the maximum of a multivariate polynomial inside a convex polytope. We show that there is no polynomial time approximation algorithm for this problem, even one with a very poor guarantee, unless P = NP. We show that even when the polynomial is quadratic (i.e. quadratic programming) there is no polynomial time approximation unless NP is contained in quasi-polynomial time.Our results rely on recent advances in the theory of interactive proof systems. They exemplify an interesting interplay of discrete and continuous mathematics—using a combinatorial argument to get a hardness result for a continuous optimization problem.     

The synthesis and characterization of calix[4]arene based azo dyes

A series of azocalix[4]arene dyes (1–7) were prepared by linking 2,4-di-chloroaniline, 2,4,5-tri-chloroaniline, 2,4-di-nitroaniline, 2-nitro p-toluidin, 4-nitro o-toluidin, 5-nitro o-toluidin and sulfanilic acid, to calix[4]arene through a diazo-coupling reaction. These compounds were characterized by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, MALDI-TOF, UV–Vis., DSC, and DTA. The absorption properties of the synthesized dyes were studied and the application of the water soluble dye on cotton and wool was discussed. Solvent based inks were investigated and the fastness properties of formulated inks were also discussed.     

Synthesis and Application of 2-Arylazo-3-Cyano Thieno [2,3-b]Naphthoquinones

The paper describes the synthesis of 2-amino-3-cyanothieno[2,3-b]naphthoquinone and its utilisation to prepare range of azo disperse dyes. These novel arylazo dyes were studied with respect to their color and constitution relationship. Application of these dyes on polyester fibres and their fastness properties were stated. These dyes were characterised by PMR, IR and visible absorption spectra.     

Development and Validation of a Stability Indicating LC Method for the Determination of Faropenem in Pharmaceutical Formulations

A simple, selective and sensitive stability indicating LC method has been developed and validated for the determination of faropenem in bulk drug and pharmaceutical formulations in the presence of degradation products. The separation was achieved by using an isocratic mobile phase mixture of acetate buffer of pH 3.5 and methanol (65:35, v/v) and 250 mm × 4.6 mm I.D., 5 μm particle size SGE make Wakosil C-18 AR column at flow rate of 1.0 mL min^?1 with detection at 305 nm. The retention time of faropenem is 6.63 min and was linear in the range of 5–75 μg mL^?1 (r = 0.9999). The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation and was found to be unstable in all the stress conditions. The proposed method was successfully employed for quantification of faropenem in bulk drug and its pharmaceutical formulations.