Synthesis of the Zn1.9Cu0.1SiO4 pigment via the sol–gel and coprecipitation methods

Journal of Sol-Gel Science and Technology - The Zn1.9Cu0.1SiO4 pigment was obtained by two variants of “soft” chemistry methods: using sol–gel synthesis in ethanol from TEOS and...     

Preparation of cruciferous phytoalexin related metabolites, (−)-dioxibrassinin and (−)-3-cyanomethyl-3-hydroxyoxindole, and determination of their absolute configurations by vibrational circular dichroism (VCD)

Cruciferous phytoalexin related metabolites, (−)-dioxibrassinin (1) and (−)-3-cyanomethyl-3-hydroxyoxindole (2) were prepared from isatin as racemates and were resolved by chiral HPLC. Their absolute configurations were determined by the new chiroptical technique, vibrational circular dichroism (VCD), as well as by the conventional electronic circular dichroism (ECD). It is concluded that the absolute configurations of the naturally occurring (−)-1 and (−)-2 are both S.     

Facile catalyzed acylation of heteroatoms using BiCl3 generated in situ from the procatalyst BiOCl and acetyl chloride

Acylation of a variety of alcohols, phenols, aliphatic and aromatic amines, a thiol and a thiophenol proceeds efficiently using BiCl₃ generated in situ from the procatalyst BiOCl and acetyl chloride in a solvent or under solventless conditions, furnishing the corresponding acylated derivatives in very good to excellent yields.     

A simple method for preparing a diamino cellulose disk from a dialdehyde cellulose disk by reductive amination using 2-picoline-borane

Cellulose - A method for the preparation of dialdehyde cellulose disks (DACD) and subsequent diamino cellulose disks (DAmCD) was developed. DACD was prepared by oxidizing filter paper with sodium...     

Synthesis of polymer microsphere-supported chiral pyrrolidine catalysts by precipitation polymerization and their application to asymmetric Michael addition reactions

Polymer microsphere-supported chiral pyrrolidine catalysts were successfully synthesized by a precipitation polymerization incorporating a methacrylate monomer bearing chiral N-Boc-pyrrolidine moiety, followed by removal of the N-Boc groups. The resulting polymeric catalysts were applied to the asymmetric Michael addition reactions of aldehydes with alkyl vinyl ketones. The effects of the comonomer, the molar ratios within the catalyst, the catalyst loading, the temperature, and the solvent on the catalytic performance were investigated in detail. The reactions were found to proceed smoothly in the absence of a solvent. A hydrophobic polystyrene-based chiral pyrrolidine catalyst exhibited high reactivity (up to 97% yield) and enantioselectivity (up to 95% ee) during these reactions. The catalyst could also be recovered and reused up to five times without significant loss of activity.     

NMR spectroscopic study of the Murex trunculus dyeing process

It is widely accepted that indigo dyes derived from Murex trunculus were used to produce the biblical dyes tekhelet and argaman. We describe a method of following the debromination of natural leucoindigos and their binding to wool using NMR spectroscopy. Debromination is observed prior to reaction with the wool and prior to oxidation. Binding to the wool is shown to occur prior to oxidation. NMR allows the dyeing process to be followed. This, in principle, could be used to correct problems during dyeing that would increase the reliability of the process.     

Uniform directional alignment of single-walled carbon nanotubes in viscous polymer flow

In this work, we probed the effects of shear flow on the alignment of dispersed single-walled carbon nanotubes in polymer solutions. Two different systems were compared: Single-walled carbon nanotubes dispersed using an anionic surfactant and single-walled carbon nanotubes dispersed using an anionic surfactant and a weakly binding polymer. It was determined that the addition of the weakly binding polymer increased the degree of dispersion of the carbon nanotubes and the ability to induce their alignment when subjected to shear forces.     

FTIR characterization of the reactive interface of cobalt oxide nanoparticles embedded in polymeric matrices

Fourier transform infrared spectroscopy (FTIR) was used as a novel characterization method to determine the properties of the interface that developed when cobalt oxide nanoparticles were self-assembled in a poly(methyl methacrylate) (PMMA) matrix. The method employed the distinct changes that were observed in the infrared spectra of the polymer upon adsorption onto the cobalt oxide nanoparticles, allowing a quantitative determination of the average number of contact points that the average polymer chain formed with the surface of a cobalt oxide nanoparticle of average size. The results obtained with this method compared favorably to those obtained by the coupling of transmission electron microscopy (TEM) experiments with thermogravimetric analysis (TGA). On the basis of both methods, we concluded that the interfacial region created between the cobalt oxide nanoparticles and PMMA is extremely sensitive to the chain length, i.e., the number of anchor points and the density of the polymer layer increase with chain molecular weight. At molecular weights of approximately 250,000, the density of the polymer layer saturates at a value that correspond to that of very thin PMMA films.     

Glycation sites in neoglycoglycoconjugates from the terminal monosaccharide antigen of the O‐PS of Vibrio cholerae O1, serotype Ogawa,and BSA revealed by matrix‐assisted laser desorption–ionization tandem mass spectrometry

We present the MALDI‐TOF/TOF‐MS analyses of various hapten–bovine serum albumin (BSA) neoglycoconjugates obtained by squaric acid chemistry coupling of the spacer‐equipped, terminal monosaccharide of the O‐specific polysaccharide of Vibrio cholerae O1, serotype Ogawa, to BSA. These analyses allowed not only to calculate the molecular masses of the hapten–BSA neoglycoconjugates with different hapten–BSA ratios (4.3, 6.6 and 13.2) but, more importantly, also to localize the covalent linkages (conjugation sites) between the hapten and the carrier protein. Determination of the site of glycation was based on comparison of the MALDI‐TOF/TOF‐MS analysis of the peptides resulting from the digestion of BSA with similar data resulting from the digestion of BSA glycoconjugates, followed by sequencing by MALDI‐TOF/TOF‐MS/MS of the glycated peptides. The product‐ion scans of the protonated molecules were carried out with a MALDI‐TOF/TOF‐MS/MS tandem mass spectrometer equipped with a high‐collision energy cell. The high‐energy collision‐induced dissociation (CID) spectra afforded product ions formed by fragmentation of the carbohydrate hapten and amino acid sequences conjugated with fragments of the carbohydrate hapten. We were able to identify three conjugation sites on lysine residues (Lys235, Lys437 and Lys455). It was shown that these lysine residues are very reactive and bind lysine specific reagents. We presume that these Lys residues belong to those that are considered to be sterically more accessible on the surface of the tridimensional structure. The identification of the y‐series product ions was very useful for the sequencing of various peptides. The series of a‐ and b‐product ions confirmed the sequence of the conjugated peptides. Copyright © 2010 John Wiley & Sons, Ltd.     

Sol-gel synthesis of hydrous ruthenium oxide nanonetworks from 1,2-epoxides

Hydrous ruthenium oxide (RuO₂·xH₂O) xerogels were synthesized through the addition of a 1,2-epoxide, propylene oxide, to commercial hydrated ruthenium chloride, “RuCl₃·xH₂O,” in ethanol. After a blue-black monolithic gel formed in 4 h, the samples were allowed to age for 24 h and were dried in ambient conditions. The dried samples were then characterized by XPS, XRD, DTA and TGA. XPS showed the Ru(3d_5/2) peak at a binding energy of 281.7 eV, corresponding to that of hydrous ruthenium oxide. XRD data revealed the synthesized material as amorphous. Heating the sample in inert atmospheres caused the complete reduction of the oxide to the zero-valent state, whereas heating the sample in air resulted in both crystalline anhydrous RuO₂ and zero-valent ruthenium, depending on the method of heating. DTA traces showed an endotherm ending at 150 °C, corresponding to the loss of coordinated water, as well as two higher temperature crystallization exotherms when the sample was heated in both inert and oxygen-rich atmospheres. TGA runs also confirmed the complete reduction of the hydrous oxide when heated in nitrogen below 270 °C and the formation of anhydrous ruthenium oxide when heated in air, confirming the XRD results.