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At least 109 records · Page 6Linked to original sources
PubMed2002

Determination of the constants of affinity of FeCl3, CuCl2, and ZnCl2 for a nitrogen-containing organosilane bonded on Al2O3-cellulose acetate hybrid material surface from ethanol solution.

This work describes the preparation and characterization of a cellulose acetate fiber coated with Al(2)O(3), resulting in the organic-inorganic hybrid Cel/Al(2)O(3). Furthermore, the hybrid was modified by attaching organofunctional groups by reaction with the precursor reagents (RO)(3)Si(CH(2))(3)L (L=NH(2), NH(CH(2))(2)NH(2), NH(CH(2))(2)NH(CH(2))(2)NH(2), and N(2)C(3)H(3) (imidazole)), resulting in Cel/Al(2)O(3)/Si(CH(2))(3)NH(2) (1), Cel/Al(2)O(3)/Si(CH(2))(3)NH(CH(2))(2)NH(2) (2), Cel/Al(2)O(3)/Si(CH(2))(3)NH(CH(2))(2)NH(CH(2))(2)NH(2) (3), and Cel/Al(2)O(3)/Si(CH(2))(3)N(2)C(3)H(3) (4). The amounts of attached organofunctional groups were (in mmol per gram of the material) 1=1.90, 2=1.89, 3=1.66, and 4=1.35. The isotherms of adsorption of FeCl(3), CuCl(2), and ZnCl(2) by Cel/Al(2)O(3)/Si(CH(2))(3)L from ethanol solutions were obtained at 298 K. Accurate estimates of the specific sorption capacities and the heteregeneous stability constants of the immobilized metal complexes were determined with the aid of several computational procedures. It is shown that the sorptional capacities are much less than the concentrations of the attached organofunctional groups. As all sorption isotherms are fitted properly with the Langmuir isotherm equation, the effects of the energetic heterogeneity and the lateral interactions do not affect the chemisorption equilibria. The heterogeneous stability constants of the immobilized complexes are fairly high, which provides efficient removal of the metal ions from solutions by the hybrid materials.

Adsorption↗
PubMed2004

Group-selective ring-closing enyne metathesis: concentration-dependent selectivity profile of alkynylsilyloxy-tethered dienynes.

Highly group-selective ring-closing metathesis of alkynylsilyloxy-tethered dienynes was achieved by using Grubbs first- and second-generation catalyst. The remarkable selectivity increase at higher concentration for differentiating between two alkene moieties in nearly identical steric and stereoelectronic environments is believed to be the result of a higher ring-closure rate for smaller-sized ring formation under rapid pre-equilibration of the two alkylidene species generated from either alkene moiety.

Alkenes↗
PubMed2004

Catalytic asymmetric synthesis of alpha-amino phosphonates using enantioselective carbon-carbon bond-forming reactions.

We have developed highly enantioselelctive reactions of silicon enolates with N-acyl-alpha-iminophosphonates leading to optically active alpha-amino phophonates. A copper (II)-diamine complex was shown to be effective in this reaction, and high levels of yield and selectivity were achieved. It is noteworthy that this reaction opens a way to various biologically important, optically active alpha-amino phosphonate derivatives.

Amines↗
PubMed1999

Synthesis of four diastereomeric 3,5-dialkoxy-2,4-dimethylalkanals by a simple extension of the non-aldol aldol process to bis(propionates).

[formula: see text] The synthesis of all four diastereomers of bis(propionates), 3,5-dialkoxy-2,4-dimethylalkanals, by non-aldol aldol chemistry is described. The epoxy alcohols (3, 4) were converted into the mesylates (9, 11) which were cleanly rearranged to the desired 3,5-bis(oxygenated)-2,4-dimethylalkanals (10, 12) in high yield. The epoxy mesylates (13, 16) gave the desired products (14, 17) in good yield on treatment with TMSOTf and a hindered base.

Aldehydes↗
PubMed2000

Dianion aggregates derived from lithiation of N-silyl allylamine.

[reaction: see text] Three different N-silyl-protected allylamines, i.e., N-TMS, N-TBDMS, and N-TIPS allylamine, were lihtiated by reaction with excess n-butyllithium. Crystallization of the resulting dianions and X-ray structure determination yields three uniquely different aggregates.

Allylamine↗
PubMed2004

Fine-tuning the degree of organic functionalization of mesoporous silica nanosphere materials via an interfacially designed co-condensation method.

A synthetic method that can fine tune the amount of chemically accessible organic functional groups on the pore surface of MCM-41 type mesoporous silica nanosphere (MSN) materials has been developed by electrostatically matching various anionic organoalkoxysilanes with the cationic cetyltrimethylammonium bromide micelles in a base-catalyzed condensation reaction of tetraethoxysilane.

Anions↗
PubMed1996

(2aS,3S,6S,7S,7bR)-7-[(dimethylphenyl)-silyl]-2-oxo-6-[(1R,2S)-2- phenylcyclo-hexyloxy]-2a,3,6,7,7a,7b-hexahydro-2H-1,4,5-trioxa-4a- azacyclopenta[cd]indene-3-carboxylic acid 1-methylethyl ester.

The structure of the title compound, C31H39NO7Si, was determined and found to be a fused tricyclic nitroso acetal. Remarkable features include a twist-boat conformation of the tetrahydro-1,2-oxazine ring and a highly pyramidalized N atom [Sigma (angles) = 310.6(6) degrees]. Three of the contiguous stereocenters in the nitroso acetal are of the same correct relative and absolute configuration as is found in (+)-crotanecine.

Crystallography, X-Ray↗
PubMedDate not supplied

[Preclinical toxicological study of the new enterosorbent noolit].

The safety of the new enterosorbent noolit has been evaluated within the framework of its preclinical characterization. Single introduction of noolit to rats and mice (females and males) in maximum doses for intragastric administration (5.0 - 20.0 g/kg) does not lead to the loss of experimental animals. Single administration of large doses (5 - 40 times the effective dose) can reduce the growth of the total body weight and lead to the development of nonlethal pathological changes of hemopoietic organs, which is manifested by a weak regenerative anemia (5% of cases); neutrophile, eosinophile, and basophile leukocytosis (3% of cases); and a decrease in the glucose level in blood serum. In chronic experiments on rabbits, the administration of noolit for 3 months in a dose of 0.5 and 2.0 g/kg (2 and 8 times that recommended for humans) did not reveal any toxic action on the functional and morphological state of the main systems and organs (blood, liver, kidneys, lungs, heart, gastrointestinal tract, sex organs, etc.).

Aluminum Oxide↗
PubMed1990

[Possible mechanisms of anti-ulcer action of silatranes].

A stimulating effect of methylethyl(silatrane-I-ilmethyl)-sulphonium iodides, 1-(ethoxy)silatranes and 1-(chloromethyl)silatrane on the processes of rat test acetate ulcer healing is studied. Silatranes efficiency is not inferior to oxyferriscorbone and exceeds that of methacil. It is shown that all preparations inhibit the processes of lipids peroxidation in the blood, in liposomes and stomach tissue.

2,3-Diketogulonic Acid↗
PubMedDate not supplied

[Changes in the periodontium in prolonged hypodynamia and the use of biphosphanates and silatrane for the purpose of their prevention].

Forty-day hypodynamia caused by "hanging" rats on a special stand with discontinuance of the status function of the hind limbs and partial maintenance of the supporting function of the front limbs led to progressive atrophic changes in the alveolar process of the animals' jaws, which were accompanied by changes of the mineral phase manifested by diminished parameter of microfirmness. Atrophy of the alveolar process in hypodynamia was attended by marked tissue changes in the form of dentogingival pockets, widening of the periodontal fissure, and intensified resorption of the interradicular and interalveolar septa of the molars.

Animals↗
PubMedDate not supplied

[Functionalized nanocomposite coating of a glass surface for oligonucleotide immobilization].

A new type of coating for manufacturing DNA chips was constructed of the basis of an organic-inorganic nanocomposite based on the polyvinylbutyral-tetraethoxysilane copolymer. The organosilicon composite was functionalized by introduction of ethanolamine vinyl ether copolymers, which contain amino groups and anchor vinyloxide units capable of reacting with silanol groups of the nanocomposite. The resulting coatings form a film on glass slides with a high surface density of amino groups (up to 700 groups/nm2) suitable for three-dimensional immobilization of oligonucleotides. The use of bifunctional reagents (e.g., phenylene diisothiocyanate) for the attachment of oligonucleotides bearing amino linkers to the amino-containing surface provides an immobilization density of 0.5-1.6 pmol/mm2. Immobilization with a higher density (10-12 pmol/mm2) was achieved for attachment to amino-containing glass slides upon the use of oligonucleotides containing selectively activated terminal phosphate groups. The activation of oligonucleotides was carried out with the triphenylphosphine-dithiodipyridine pair in the presence of dimethylaminopyridine N-oxide. The resulting DNA chips were shown to be useful in principle for DNA detection.

DNA↗
PubMed2006

Synthesis of magnetic nanoparticles and their application to bioassays.

Magnetic nanoparticles have been attracting much interest as a labeling material in the fields of advanced biological and medical applications such as drug delivery, magnetic resonance imaging, and array-based assaying. In this review, synthesis of iron oxide magnetic nanoparticles via a reverse micelle system and modification of their surface by an organosilane agent are discussed. Furthermore, as a practical biological assay system, the magnetic detection of biomolecular interactions is demonstrated by using the combination of a patterned substrate modified with a self-assembled monolayer and the magnetic nanoparticles.

Biotin↗
PubMed2003

Stereodirected synthesis of aryl alpha-C-glycosides from 2-O-arylsilyl-glucopyranosides.

[reaction: see text] An efficient procedure for the stereoselective synthesis of aryl alpha-C-glycosides is presented. The key step of the method is the intramolecular delivery of the aryl group from a 2-O-aryldialkylsilyl substituent to the anomeric carbon by an electrophilic ipso-desilylation; this process leads exclusively to the product having the 1,2-cis configuration.

Benzyl Compounds↗
PubMed2005

Synthesis of the A-B subunit of angelmicin B.

[reaction: see text] An efficient synthesis of the tricyclic A-B subunit 2 of angelmicin B is described. A formal three-component coupling of aldehydes 4 and 6 with gamma-silylallylborane 7 was employed to assemble the tetrahydrofuranyl core of 2, a strategy highlighted by the stereoselective [3 + 2] annulation of allylsilanes 5a/5b with aldehyde 4. The efficiency of the [3 + 2] annulation was greatly improved by using the allylic benzhydryldimethylsilane 5b compared to the allylic phenyldimethylsilane 5a.

Aldehydes↗