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  • 1
    ISSN: 0170-2041
    Keywords: L-Xylose ; 2-Deoxy-L-xylo-hexose ; Enzymatic syntheses ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemo-Enzymatic Synthesis of Carbohydrates: The Preparation of L-Xylose and 2-Deoxy-L-xylo-hexoseA synthetic approach to L-xylose (6) and 2-deoxy-L-xylo-hexose (8) has been developed. The strategy utilizes achiral starting materials and employs two enzymatic reactions to introduce the desired chiral centers. Rabbit muscle aldolase (RAMA)-catalyzed condensation of (3-phenylthio)propanal (1) with dihydroxyacetone phosphate (DHAP) affords the C-6 skeleton 2 with D-threo configuration between C-3 and C-4. Diastereoselective reduction of 2 with sorbitol dehydrogenase (SDH) introduces the final stereocenter of the tetrahydroxy derivative 3. After oxidation of sulfide 3 to the corresponding diastereotopic sulfoxides 4, L-xylose (6) is obtained by thermal elimination of phenylsulfenic acid followed by ozonolysis. 2-Deoxy-L-xylo-hexose (8) is yielded from 4 by a Pummerer rearrangement and subsequent reductive deprotection (DI-BAL-H) of the rearrangement product 7.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0170-2041
    Keywords: Sialic acid, 5-azido- ; Neuraminic acid, N-acyl derivatives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This communication describes the first synthesis of the α-methyl ketoside of an N-unprotected neuraminic acid in the form of its methyl ester (Neu5NH21Me-α-2Me) (5a). This compound is a valuable intermediate for the synthesis of unnatural N-substituted sialic acids. Syntheses of Neusmyristoyl1me-α-2Me (5b) and Neuscyclopropanoyl1me-α-2Me (5c) are presented.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 18 (1979), S. 377-392 
    ISSN: 0570-0833
    Keywords: Orbital symmetry ; Woodward-Hoffmann rules ; Kinetics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of molecular symmetry on reaction rates is examined with an approach in which reactions are viewed as electronic transitions between states of reacants and products (described, in turn by quasiadiabatic potential surface). The moleculer Hamiltonian is used to derive selection rules for these transitions. The complete Hamilatonian has no useful symmetery. Neglect of non-Born-Oppenheimer and spin-orbit terms (and of other angular momentum coupling terms) leads to an apporixmate Hamiltonian and to selection rules which from the basis of the Woodward-Hoffmann rules. This apporch provides an alternative to the adiabatic potantial surfaces, reaction coordinates, and transition state theory used in more familiar discussions of the Woodward-Hoffmann rules. Further, it provides a particulary clear method for discussing violations of these symmetry rules, and for differentiating concerted and nonconcerted reactions.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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