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  • 1
    Electronic Resource
    Electronic Resource
    Enzymes in Organic Synthesis: Application to the Problems of Carbohydrate Recognition (Part 1)Part 2: Angew. Chem. 1995, 107, Nr. 5; Angew. Chem. 1995, 34, No. 5. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 34 (1995), S. 412-432 
    Details
    ISSN: 0570-0833
    Keywords: carbohydrates ; enzymes ; organic synthesis ; Synthetic methods ; Enzymes ; Carbohydrates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbohydrates on cell surfaces are information molecules. Although only seven or eight monosaccharides are commonly used as building blocks in mammalian systems, the multifunctionality of these monomers can lead to the assembly of an immense variety of complex structures. Millions of different tetrasaccharide structures, for example, can be constructed from this small number of building blocks, if branching, the stereochemistry of glycosidic linkages, and the modification of hydroxyl and amino groups are taken into consideration. Oligosaccharides therefore represent an effective class of biomolecules that code for a vast amount of information required in various biological recognition processes, such as intercellular communication, signal transduction, cell adhesion, infection, cell differentiation, development and metastasis. The pace of development of pharmaceuticals based on carbohydrates has, however, been slower than that based on other classes of biomolecules. Part of the reason is the lack of technologies for the study of complex carbohydrates. There is no method to amplify oligosaccharides for sequence analysis. There is no machine available for automated synthesis of oligosaccharides. In addition, the possibly poor bioavailability and difficulties in the large-scale synthesis of carbohydrates have undoubtedly contributed to this slow pace. The enzymatic and chemoenzymatic methods, especially those based on aldolases and glycosyltransferases, described here appear to be useful for the synthesis of mono- and oligosaccaharides and related molecules. Further advances in glycobiology will probably lead to the development of new technologies for the study of carbohydrate recognition and for the synthesis of bioactive carbohydrates and mimetics to control the recognition processes.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199504121
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  • 2
    Electronic Resource
    Electronic Resource
    Enzymes in Organic Synthesis: Application to the Problems of Carbohydrate Recognition (Part 2)Part 1: Angew. Chem. 1995, 107, 453; Angew. Chem. Int. Ed. Engl. 1995, 34, 412. The numbering of the sections, references, schemes, and Tables follows on from Part 1. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 34 (1995), S. 521-546 
    Details
    ISSN: 0570-0833
    Keywords: carbohydrates ; enzymes ; organic synthesis ; Synthetic methods ; Enzymes ; Carbohydrates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recognition of carbohydrates by proteins and nucleic acids is highly specific, but the dissociation constants are relatively high (generally in the mM to high μM range) because of the lack of hydrophobic groups in the carbohydrates. The high specificity of this weak binding often comes from many hydrogen bonds and the coordination of metal ions as bridge between sugars and receptors. Though weak hydrophobic interactions between sugars and proteins have also been identified, the unique shape of a complex carbohydrate under the influence of anomeric and exo anomeric effects (the glycosidic torsion angles are therefore often not flexible but are typically somewhat restricted) and the topographic orientation of the hydroxyl and charged groups contribute most significantly to the recognition process. Studies on the structure-function relationship of a complex carbohydrate therefore require deliberate manipulation of its shape and functional groups, and synthesis of oligosaccharide analogs from modified monosaccharides is often useful to address the problem. The availability of various monosaccharides and their analogs for the synthesis of complex carbohydrates together with the information resulting from structural studies (such a NMR or X-ray studies on sugar-protein complexes) will certainly provide a basic understanding of complex carbohydrate recognition. An ultimate goal is to develop simple and easy-to-make non-carbohydrate molecules that resemble the active structure involved in carbohydrate-receptor interaction or the transition-state of an enzyme-catalyzed transformation (for example, glycosidase or glycosyltransferase reactions) and have the approprite bioavailability to be used to control the carbohydrate function in a specific manner. In part one of this review we described various enzymatic approaches to the synthesis of monosaccharides, analogs, and related structures. We describe in this part enzymatic and chemoenzymatic approaches to the synthesis of oligosaccarides and analogs, including those involved in E-selectin recognition, and strategies to inhibit glycosidases and glycosyltransferases.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199505211
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    Paper (German National Licenses)
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