Search results for "HILIC"
showing 10 items of 745 documents
Synthesis of β-d-mannosides from β-d-glucosides via an intramolecular Sn2 reaction at C-2
1992
Abstract The selective synthesis of β- d -mannosides was achieved by first synthesizing β- d -glucosides that carry a N -phenylcarbamoyl protecting group at O-3. These derivatives were transformed into the corresponding β- d -mannosides by intramolecular nucleophilic substitution with inversion of configuration at C-2, the O -triflyl group being the leaving group. Subsequent intramolecular attack of the neighboring carbamoyl group resulted in the formation of the 2,3-carbonate of the desired β d -mannoside.
Preformed polymers for Langmuir-Blodgett films- molecular concepts
2008
The use of preformed polymers for the preparation of Langmuir-Blodgett (LB) multilayers is reviewed. Principles for polymer self-organization are outlined and the appropriate molecular designs are discussed. Recent developments in the different classes of polymers for LB multilayers are presented, and their outstanding properties highlighted.
Design of the Biotechnological System for the Cultivation of a Polysaccharide-Producing Microorganism and Metabolites Separation
1970
This paper presents a design of the biotechnological system established for the cultivation of a polysaccharide-producing microorganism and the separation of the polysaccharide together with other metabolites. The strain used is a halophilic archaeon called Haloferax mediterranei (Mironescu et al., 2003). On designing the biotechnological system, some requirements are important: The recipients and the pipes must be resistant to the corrosion action of the cultivation substrate very rich in NaCl (125 to 150 g/l); A command and control system for pH, temperature and substrate and inoculum feeding is necessary; A system for monitoring dissolved oxygen and gases evacuated from the bioreactor (O…
(Co-)solvent selection for single-wall carbon nanotubes: best solvents, acids, superacids and guest-host inclusion complexes.
2011
Analysis of 1-octanol-water, cyclohexane-water and chloroform (CHCl(3))-water partition coefficients P(o-ch-cf) allows calculation of molecular lipophilicity patterns, which show that for a given atom log P(o-ch-cf) is sensitive to the presence of functional groups. Program CDHI does not properly differentiate between non-equivalent atoms. The most abundant single-wall carbon nanotube (SWNT), (10,10), presents a relatively small aqueous solubility and large elementary polarizability, P(o-ch-cf) and kinetic stability. The SWNT solubility is studied in various solvents, finding a class of non-hydrogen-bonding Lewis bases with good solubility. Solvents group into three classes. The SWNTs in so…
Molecular aggregation in selected crystalline 1:1 complexes of hydrophobicD- andL-amino acids. IV. TheL-phenylalanine series
2009
The amino acid L-phenylalanine has been cocrystallized with D-2-aminobutyric acid, C(9)H(11)NO(2).C(4)H(9)NO(2), D-norvaline, C(9)H(11)NO(2).C(5)H(11)NO(2), and D-methionine, C(9)H(11)NO(2).C(5)H(11)NO(2)S, with linear side chains, as well as with D-leucine, C(9)H(11)NO(2).C(6)H(13)NO(2), D-isoleucine, C(9)H(11)NO(2).C(6)H(13)NO(2), and D-allo-isoleucine, C(9)H(11)NO(2).C(6)H(13)NO(2), with branched side chains. The structures of these 1:1 complexes fall into two classes based on the observed hydrogen-bonding pattern. From a comparison with other L:D complexes involving hydrophobic amino acids and regular racemates, it is shown that the structure-directing properties of phenylalanine closel…
Photoaffinity cross-linking of F1ATPase from the thermophilic bacterium PS3 by 3′-arylazido-β-alanyl-2-azido ATP
1989
AbstractThe photoactivatable bifunctional 3′-arylazido-β-alanyl-2-azido ATP (2,3′-DiN3ATP) has been applied to study the localization of the nucleotide-binding sites of coupling factor 1 (F1ATPase, TF1) from the thermophilic bacterium PS3 by photoaffinity cross-linking. UV irradiation of TF1 in the presence of 2,3′-DiN3ATP results in the nucleotide-dependent formation of various higher molecular mass cross-links formed by two, three or even four α- and/or β-subunits. The differences observed upon photoaffinity cross-linking by the bifunctional 2-azido ATP or 8-azido ATP analog are discussed. They are probably due to the varied maximal distance between both azido groups, or to the different …
Preparation of 9a-Fluorinated Sesquiterpenic Drimanes and Evaluation of Their Antifeedant Activities
2010
19 pages, figures, and tables statistics.
Fluorinated Heterocyclic Compounds. An Expedient Route to 5-Perfluoroalkyl-1,2,4-triazoles via an Unusual Hydrazinolysis of 5-Perfluoroalkyl-1,2,4-ox…
2003
The hydrazinolysis reaction of 5-perfluoroalkyl-1,2,4-oxadiazoles has been investigated. Nucleophilic addition of the reagent to the C(5)-N(4) double bond of the oxadiazole ring, followed by ring-opening and then ring-closure involving the beta-nitrogen atom of the hydrazino moiety and the C(3) of the oxadiazole ring, explains the formation of 5-perfluoroalkyl-1,2,4-triazoles as final products. Useful applications in synthesis of this uncommon hydrazinolysis can be claimed.
Reactivity of the carbon-carbon double bond towards nucleophilic additions. A dft analysis
2004
Abstract The global and local electrophilicity indexes have been used to characterize the reactivity pattern of the CC double bond towards nucleophilic addition reactions. A wide family of molecules including ketones, esters, anhydrides, nitriles and nitrocompounds containing appropriate substitution on the CC double bond have been classified within an unique scale of reactivity. The predictive capability of the theoretical model is tested against a series of benzylidenemalononitriles and substituted α-nitrostilbenes.
A new strategy for the synthesis of fluorinated 3,4-dihydropyrimidinones
2009
A new family of 3,4-dihydropyrimidinones (DHPMs) bearing fluorinated substituents at C6 have been prepared from gem-difluorinated nitriles, alkyl 3-butenoates and iso(thio)cyanates. This novel Biginelli-type process relies on the gamma-addition of the ester-derived enolate to fluorinated nitriles. A tandem nucleophilic addition aza-Michael reaction sequence completes the synthetic process. (C) 2009 Elsevier B.V. All rights reserved.