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  • General Chemistry  (4)
  • Analytical Chemistry and Spectroscopy  (1)
  • Wiley-Blackwell  (5)
  • Hindawi
  • 1
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2591-2597 
    ISSN: 1434-193X
    Schlagwort(e): Cascade molecules ; Dendrimers ; Chirality ; Amides ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 1434-193X
    Schlagwort(e): Mitsunobu reaction ; Desymmetrization ; Cyclic nitrones ; Polyhydroxyindolizidines ; Glycosidase inhibitors ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 1434-193X
    Schlagwort(e): Alkylidenecyclopropanes ; Palladium ; Intramolecular 1,3-dipolar cycloaddition ; Thermal rearrangement ; Pyrrolo[3,4-b]pyridine ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 1434-193X
    Schlagwort(e): Parallel kinetic resolution ; Double asymmetric induction ; Chiral cyclic nitrones ; Cycloadditions ; Asymmetric synthesis ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: -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.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 1H, 13C, 14N and 199Hg NMR data were obtained for organomercury fulminates, RHgCNO (R — Me, Ph, CNO). The relatively slow relaxation processes effective for the quadrupolar nitrogen muclei of these compounds allow the detection of 199Hg—14N scalar coupling constants. This feature is ascribed to the presence of low electric field gradients around the 14N nucleus, owing to the presence of the mercury atom. In mercury fulminate, the 199Hg nucleus appears to be coupled with two equivalent 14N nuclei, thus indicating the existence of a covalent structure Hg(CNO)2 in solution.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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