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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2591-2597 
    ISSN: 1434-193X
    Keywords: Cascade molecules ; Dendrimers ; Chirality ; Amides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the first and second generation of enantiopure dendrimers based on a chiral trans-3,4-dihydroxypyrrolidine is reported. Benzenepolycarboxylic acids were used as central nucleus to afford linear and radial growth, and terephthalic acid was used as spacer between the pyrrolidine nuclei. The analysis of the chiroptical properties ([α]D, circular dichroism) of these new dendrimers suggests that those with radial growth present a self organisation of chiral units.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-193X
    Keywords: Alkylidenecyclopropanes ; Palladium ; Intramolecular 1,3-dipolar cycloaddition ; Thermal rearrangement ; Pyrrolo[3,4-b]pyridine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several alkylidenecyclopropanes have been synthesized in high yields and optical purity by palladium(0)-catalyzed substitution of 1-tosyloxy-1-vinyl cyclopropane using N-tosylamino esters or glycolic ester as nucleophiles. The new alkylidenecyclopropanes were transformed to the corresponding nitrones without loss of optical purity, except in the case of the phenylglycine derivative. The alkylidenecyclopropane nitrones underwent smooth in situ intramolecular cycloaddition with a stereoselectivity that was moderate with most substituted substrates, but complete with phenylglycine and proline derivatives. The spirocyclopropane isoxazolidines were transformed by selective thermal rearrangements in octahydro-2H-pyrrolo[3,4-b]pyridin-7-ones and octahydrofuro[3,4-b]pyridin-7-one, uncommon ring systems resembling biologically active natural and nonnatural products. An example of the extension of the process to an alkylidenecyclopropane nitrile oxide is also reported.
    Additional Material: 2 Ill.
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  • 3
    ISSN: 1434-193X
    Keywords: Mitsunobu reaction ; Desymmetrization ; Cyclic nitrones ; Polyhydroxyindolizidines ; Glycosidase inhibitors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A protocol is presented for a completely enantioselective formal desymmetrization of Cs-symmetric diols by monoprotection of the corresponding enantiopure C2 diols, followed by an inversion of configuration by a Mitsunobu reaction (“Mitsunobu trick”). Its application to the unprecedented synthesis of enantiopure cis-3,4-dihydroxypyrroline N-oxides, employed in the enantiodivergent synthesis of two selectively protected 1,2,7-trihydroxyindolizidines, is also reported.
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  • 4
    ISSN: 1434-193X
    Keywords: Parallel kinetic resolution ; Double asymmetric induction ; Chiral cyclic nitrones ; Cycloadditions ; Asymmetric synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Cycloadditions of hydroxylated enantiopure pyrroline N-oxides to 1,2-glycals display high double-asymmetric induction. The selectivity is controlled by the stereochemistry at C-3 of the glycal. A parallel kinetic resolution experiment with a racemic cis-dihydroxypyrroline N-oxide allowed the synthesis of two different pseudo imino-C-disaccharides precursors in a completely enantiopure form, totally avoiding the formation of minor cycloadducts.
    Type of Medium: Electronic Resource
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