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  • Macrocycles  (1)
  • N-Acyliminium  (1)
  • Pipecolic acid derivative  (1)
  • Strained compounds  (1)
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Erscheinungszeitraum
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  • 1
    Digitale Medien
    Digitale Medien
    Efficient Preparation of a Highly Strained Eleven-Membered Ring (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 155-163 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Macrocycles ; Cyclizations ; Strained compounds ; Ketophosphonate ; Iodoalkyne ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Two strategies have been explored to build the highly strained eleven-membered ring 2, a potential precursor for the biosynthetic key intermediate of the protoilludane family: an intramolecular Horner-Wadsworth-Emmons olefination and an intramolecular Nozaki-Hiyama-Kishi type-ring closure.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Highly Stereoselective trans Addition of π-Type Nucleophiles to a Bicyclic N-Acyliminium Ion - Application to the Synthesis of Indolizidine and Pyrrolizidine Alkaloids (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1955-1963 
    Details
    ISSN: 1434-193X
    Schlagwort(e): N-Acyliminium ; Pyrrolidine ; Indolizidine ; Pyrrolizidine ; Stereoselective ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Enantiopure bicyclic 5-ethoxytetrahydropyrrolo[1,2-c]oxazol-3-one 1b was prepared in two steps from the known tosylate 4, which is readily available from (S)-pyroglutamic acid. Trapping of the N-acyliminium ion (I), generated in situ from 1b in the presence of Lewis acid, with various silylated π-type nucleophiles gave rise selectively to trans adducts 2. The usefulness of this stereoselective access to trans-2,5-disubstituted pyrrolidines was illustrated by formal syntheses of 3,5-disubstituted indolizidine toxins, starting from 5-allyltetrahydropyrrolo[1,2-c]oxazol-3-one 2a. Moreover, an enantiodivergent synthesis of the pyrrolizidine alkaloids (+) and (-)-xenovenine was achieved starting from the same chiral building block 2a.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Enantioselective Synthesis of an Allenyl Derivative of Pipecolic Acid (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2461-2465 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Iminium ion ; Propargylsilane ; Pipecolic acid derivative ; Amino acids ; Asymmetric synthesis ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Addition of a propargylsilane moiety onto chiral cyclic iminium ions occurs with a high level of stereoselectivity intermolecularly as well as intramolecularly. This operation generates allenic α-amino acids precursors. An isomerization leading to a 1,3-dienyl compound precludes the formation of an allenic amino acid in the acyclic series; however, this isomerization did not take place with the cyclic α-amino ester which was thus obtained with a 55 % ee. AM1 calculations explain the difference of reactivity between cyclic and acyclic compounds on a conformational basis.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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