Efficient preparation of glycoclusters from silsesquioxanes

[structure: see text] A new type of glycocluster based on polyhedral oligosilsesquioxanes (POSS) has been efficiently prepared from unprotected mannoside and lactoside employing a convergent approach of thiol-radical addition reaction. The versatility of this approach was demonstrated by functionalization of mannosides and lactosides of different-length spacers.     

Holography and string dynamics in time-dependent backgrounds

We study the dynamics of D-branes in a smooth time-dependent background. The theory on the branes is a time-dependent noncommutative field theory. We find the metric and fluxes that determine the dual holographic closed string theory. This provides a concrete example of holography in a cosmological setting.     

A novel organic intercalation system with layered polymer crystals as the host compounds derived from 1,3-diene carboxylic acids

A new type of organic intercalation system using poly(muconic acid) and poly(sorbic acid) crystals as the host compounds is described. The layered polymer crystals as the host are derived from benzyl-, dodecyl-, or naphthylmethylammonium salts of (Z,Z)-muconic or (E,E)-sorbic acids by topochemical polymerization. The subsequent solid-state hydrolysis of the resulting ammonium polymer crystals provides the corresponding carboxylic acid polymer crystals. When alkylamines are reacted with poly(muconic acid) or poly(sorbic acid) crystals dispersed in methanol at room temperature for a few hours, the intercalation proceeds to give layered ammonium polymer crystals via solid-state reactions, in which the polymers maintain a layered structure throughout. The interplanar spacing value of the polymer crystals changes according to the size of the guest molecules; that is, it exactly depends on the carbon number of the alkylamines used for each reaction of poly(muconic acid) or poly(sorbic acid) crystals. The stacking structure of alkyl chains with a tilt in the intercalated alkylammonium layers exists irrespective of the chemical and crystal structures of the host polymers. The intercalation of higher alkylamines into poly(muconic acid) crystals proceeds fast and quantitatively, while the conversion is dependent on the reaction conditions such as the structure and amount of the amine and the reaction time during the intercalation with poly(sorbic acid) crystals, due to the difference in the repeating layered structures of these polymer crystals. Some functional amines are also used as the guest molecules for this organic intercalation system.     

Determination of sulfate ester content in sulfated oligo‐ and poly‐saccharides by capillary electrophoresis with indirect UV detection

Carbohydrates having sulfate groups such as glycosaminoglycans and chemically synthesized sucrose sulfate show interesting and important biological activities. We adapted CE with indirect UV detection technique to the determination of sulfate ester in sulfated carbohydrates, which were previously hydrolyzed with HCl. The liberated sulfate ion was analyzed using a background electrolyte consisting of triethanolamine‐buffered chromate with hexamethonium bromide. Sulfate contents of glucose 3‐sulfate and sucrose octasulfate used as a model were in good agreement with theoretical values (accuracy, 95.9–96.7 and 97.4–101.9%, respectively), and relative standard deviation values run‐to‐run were 0.977 and 1.90%, respectively. We applied the method to the determination of the sulfate contents of some glycosaminoglycan samples and showed that the contents were in good agreement with those calculated from sulfur content. Copyright © 2010 John Wiley & Sons, Ltd.     

Low molecular weight aromatic compounds possessing nonflammable and flammable characteristics in calcium fluoride nanocomposite matrices after calcination at 800 °C

Calcium chloride reacted with potassium fluoride in the presence of low molecular weight aromatic compounds (ArH) such as bisphenol AF, bisphenol A, bisphenol F, biphenyl, and 1-(2-naphthyl)ethanol under alkaline conditions to afford new calcium fluoride/ArH composites. Dynamic light scattering and field emission scanning electron micrographs measurements show that these calcium fluoride/ArH composites are nanometer size-controlled fine particles and have a good dispersibility and stability in water, tetrahydrofuran, 1,2-dichloroethane, methanol, dimethyl sulfoxide, N,N-dimethylformamide, and 2-propanol. Interestingly, aromatic compounds possessing acidic hydroxyl groups in the calcium fluoride nanocomposites were found to exhibit a nonflammable characteristic even after calcination at 800 °C, although the corresponding aromatic compounds possessing neither acidic hydroxyl groups nor hydroxyl groups in the nanocomposites exhibited a usual flammable characteristic under similar conditions. In contrast, calcium fluoride/ArH nanocomposites, which were prepared under no catalytic conditions, afforded a clear weight loss corresponding to the contents of ArH in the composites to exhibit a usual flammable characteristic.

Profiling the Cell Surface Glycome of Five Fungi Using Lectin Microarray

Fungal surface glycans play roles in cell protection and interaction. Our knowledge of fungal glycans, however, is limited to model yeasts and a few medically/industrially important fungi. We evaluated the usefulness of a lectin microarray in analysis of live cell surface glycans and then applied the technique to glycome of varieties of yeast-form fungi from various phyla and subphyla. We found glycan profiles are different among and within taxonomic groups. For example, Saccharomycotina were classified into two groups, one bound to mannose-specific lectins and the other bound to galactose/N-acetylgalactosamine-specific lectins. In Basidiomycota, Pucciniomycotina yeasts were distinguished from other subphylum members in binding to fucose-specific lectins. Supplemental materials are available for this article. Go to the publisher's online edition of Journal of Carbohydrate Chemistry to view the free supplemental file.     

Conformational Stability of 2,2′-Dialkoxybenzpinacols in Solid State

Abstract

X-ray analyses of the 2,2′-dialkoxybenzpinacols have established that the previously tentative assignment of configuration is incorrect. For example, the dl-and meso-isomer of 2,2′-dimethoxy-, 2,2′-diethoxy-, and 2,2′-dibutoxybenzpinacols proved to have a rigid conformation (1aα, 1bα, 1eα) and (1aβ, 1bβ, 1cα) where hydroxy groups are always in an anti fashion, in the solid state, respectively. MM2 and semi-empirical molecular orbital calculations for possible conformations were performed, suggesting that the conformational stability of the present pinacols is controlled by repulsive gauche interactions between aryl groups associated with intramolecular hydrogen bondings.     

Determination of hyaluronic acid by high-performance liquid chromatography of the oligosaccharides derived therefrom as 1-(4-methoxy)phenyl-3-methyl-5-pyrazolone derivatives

Hyaluronic acid (HA) was digested with various kinds of depolymerizing enzymes and the products were analysed by high-performance liquid chromatography (HPLC) after derivatization with 1-(4-methoxy)phenyl-3-methyl-5-pyrazolone (PMPMP). As hyaluronate 4-glycanohydrolase (EC 3.2.1.35) from sheep testis showed a high efficiency for depolymerization, giving the tetra- and hexasaccharides abundantly, and is inexpensive, a method for the specific determination of HA was established, based on digestion by this enzyme followed by determination of the tetra- or hexasaccharide derived therefrom as the PMPMP derivatives by HPLC with UV detection. This method allowed the determination of HA in the range 0.5–50 μg with high reproducibility.     

Preparation of colloidal stable fluoroalkyl end‐capped oligomer/silver nanocomposites––application to the surface modification of traditional organic polymers with these nanocomposites

A variety of fluoroalkyl end‐capped oligomers/silver nanocomposites were prepared by the reactions of silver ions with poly(methylhydrosiloxane) in the presence of fluoroalkyl end‐capped N,N‐dimethylacrylamide oligomer, N‐(1,1‐dimethyl‐3‐oxobutyl)acrylamide oligomer, N,N‐dimethylacrylamide cooligomer containing poly(dimethylsiloxane) segments in organic media such as toluene and 1,2‐ dichloroethane. These fluorinated oligomers/silver nanocomposites thus obtained were found to exhibit clear plasmon absorption bands around 420 nm related to the formation of silver nanoparticles. In particular, these composites could display narrow plasmon absorptions around 420 nm in toluene by the addition of trioctylamine (TOA). On the other hand, the corresponding non‐fluorinated N‐(1,1‐ dimethyl‐3‐oxobutyl)acrylamide oligomer was not able to afford such a plasmon absorption under similar conditions. These fluorinated oligomers/silver nanocomposites in organic media have been found to be stable for more than 10 days. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements showed that silver nanoparticles could be effectively encapsulated into fluorinated oligomeric aggregate cores to afford colloidal stable fluorinated oligomers/silver nanocomposites. Fluorinated oligomers/silver nanocomposites were also applied to the surface modification of traditional organic polymers such as polystyrene (PSt) and poly(methyl methacrylate) (PMMA) to exhibit not only a good oleophobicity imparted by fluorine but also a higher surface antibacterial activity related to the silver nanoparticles on their surface. Copyright © 2007 John Wiley & Sons, Ltd.     

Practical, general, and systematic method for optical resolution of gem-dihalo- and monohalocyclopropanecarboxylic acids utilizing chiral 1,1'-binaphtholmonomethyl ethers: application to the synthesis of three chiral pesticides

We performed an efficient practical and systematic optical resolution method for gem-dihalo- and monohalocyclopropanecarboxylic acids and utilizing chiral 1,1'-binaphthol monomethyl ether (R)- as the key auxiliary. Direct esterification of with (R)- gave two 1R- and 1S-diastereomeric esters with marked different R(f) values, both of which were easily separated using simple column chromatography. Monodehalogenation of separated chiral esters using t-BuMgCl and cat. Co(dppe)(2)Cl(2) gave two 1,2-trans- and 1,2-cis-diastereomers with markedly different R(f) values, both of which were similarly separated using simple column chromatography. The obtained diastereomers and were easily hydrolyzed to the desired enantiopure acids (>99%) and (>99%), respectively, with recovery of (R)-, both in good to excellent yields. Utilizing the present method, important chiral agrochemicals, carpropamid and fencyclate , were readily synthesized. Pyrethroid with three asymmetric centers was efficiently synthesized in a much better yield compared with the reported method.