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Direct Construction (direct + construction)

Distribution by Scientific Domains
Chemistry83%

Selected Abstracts

ChemInform Abstract: Highly Enantioselective Relay Catalysis in the Three-Component Reaction for Direct Construction of Structurally Complex Heterocycles.

CHEMINFORM, Issue 40 2010
Chao Wang
Abstract The three-component cascade reaction, consisting of an enantioselective [4 + 2] cycloaddition reaction catalyzed by chiral phosphoric acid and a subsequent catalytic intramolecular hydroamination by gold(I) complex, provides a method to access structurally diverse julolidine derivatives. [source]

ChemInform Abstract: Zipper-Mode Double C,H Activation: Palladium-Catalyzed Direct Construction of Highly Fused Heterocyclic Systems.

CHEMINFORM, Issue 14 2008
Hiroaki Ohno
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Bromoallenes as Allyl Dication Equivalents in the Presence or Absence of Palladium(0): Direct Construction of Bicyclic Sulfamides Containing Five- to Eight-Membered Rings by Tandem Cyclization of Bromoallenes.

CHEMINFORM, Issue 22 2007
Hisao Hamaguchi
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Chemoselective Reagents for Covalent Capture and Display of Glycans in Microarrays,

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2010
Emiliano Cló
Abstract Glycobiology has made very significant progress in the past decades. However, further progress will significantly depend on the establishment of novel methods for miniaturized, high-throughput analysis of glycan,protein interactions. Robust solid-phase chemical tools and new, chemoselective reagents for biologically meaningful display of surface-immobilized glycans are likely to play a key role. Here we present four new bifunctional linkers that allow highly chemoselective capture of unprotected glycans in solution to form glycan-linker conjugates for direct construction of glycan microarrays (glycochips). The bifunctional linkers carry O -linked aminooxy moieties, some with N -substituents at one end and an amino group at the other. In addition, they contain a substituted benzene ring for UV traceability and improved purification of glycan-linker conjugates. NMR spectroscopic studies in solution proved that N -substituted aminooxy linkers provided model glycan-linker conjugates with the ,-glucopyranoside configuration, i.e. the ring-closed form required for biological recognition. Then an ensemble of glycan-linker conjugates were assembled from mannobiose, lactose, and N -acetyl-lactosamine and used for covalent printing of glycan microarrays. The stability of oximes were studied both in solution and on-chip. In solution, two of the linkers provided glycan-linker conjugates with a remarkable stability at pH 4 or higher, on-chip this relative stability was upheld. Two of the linkers, with different properties, are recommended for the glycobiology toolbox for the construction of glycan microarrays from unprotected glycans. [source]

Controller design based on similar skew-symmetric structure for nonlinear plants

ASIAN JOURNAL OF CONTROL, Issue 1 2010
Yicheng Liu
Abstract This paper proposes a novel controller design approach for nonlinear plants. A class of stable nonlinear systems with a similar skew-symmetric structure is chosen as the objective closed loop system, and two design methods are proposed with backstepping and direct construction. Compared with the conventional backstepping method, the proposed backstepping method need not construct a Lyapunov function step by step, thus the design procedure is simplified. The direct construction method can be applied to some nonlinear plants for which the conventional backstepping is not feasible; and the design can be accomplished in only one step. Furthermore, for some nonlinear plants which have a lower triangular structure with two subsystems, simpler controllers can be derived by the proposed direct construction method than those derived by backstepping design. In addition, the proposed methods are both system structure oriented, therefore their designs are more intuitive than the conventional backstepping design. Two controllers are derived for satellite attitude control by employing the proposed methods; simulation results demonstrate their effectiveness. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]

Synthesis of Fused and Linked Bicyclic Nitrogen Heterocycles by Palladium-Catalyzed Domino Cyclization of Propargyl Bromides

CHEMISTRY - A EUROPEAN JOURNAL, Issue 28 2010
Akinori Okano Dr.
Abstract The palladium(0)-catalyzed direct construction of bicyclic heterocycles is described. Treatment of propargyl bromides that have nucleophilic functional groups connected by two or three carbon atoms with catalytic [Pd(PPh3)4] affords bis-cyclization products in good yields. The desired bicyclic heterocycles can be obtained selectively when using substrates with appropriate nucleophilic groups. We also describe the reaction of a 2-alkynylazetidine derivative with a catalytic amount of [Pd(PPh3)4] under base-free conditions, which affords the same fused heterocycles as the corresponding propargyl bromides. [source]