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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 527-531 
    ISSN: 0170-2041
    Keywords: Dehydroalanine esters, N-(arylmethylene)- ; Tetrahydropyridines ; 3,6-Diazabicyclo[3.2.1]oct-2-enes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Dimerization Reaction of N-(Arylmethylene)dehydroalanine Methyl EstersN-(Arylmethylene)dehydroalanine esters are highly reactive compounds. They dimerize in a [4 + 2] cycloaddition reaction (Diels-Alder reaction) yielding rac-3,4,5,6-tetrahydropyridine derivatives 2 Which can be isolated under suitable conditions. In solution the dimers 2 tautomerize to give the enamines 3 which subsequently undergo a fast intramolecular cyclization reaction yielding the bicyclic compounds. 4. These 3,6-diazabicyclo[3.2.1]oct-2-ene derivatives 4 are formed diastereoselectively. The structure of 4 was established by X-ray analysis. The bicyclic diaminodicarboxylic esters 4 represent the stable final products of this series of transformations.
    Notes: N-(Arylmethylen)dehydroalaninester sind hochreaktive Verbindungen. Sie dimerisieren unter [4+2]-Cycloaddition (Diels-Alder-Reaktion) zu rac-3,4,5,6-Tetrahydropyridin-Derivaten 2, die unter geeigneten Bedingungen isoliert werden können. In Lösung tautomerisieren die Dimeren 2 zu Enaminen 3, die schnell intramolekular zum Bicyclus 4 reagieren. Diese 3,6-Diazabicyclo-[3.2.1]oct-2-en-Derivate 4 werden diastereoselektiv gebildet. Ihre Struktur wurde durch Röntgenstrukturanalyse geklärt. Die bicyclischen Diaminodicarbonsäureester 4 stellen die stabilen Endprodukte der gesamten Reaktionsfolge dar.
    Additional Material: 1 Ill.
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  • 2
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of N-(Arylmethylene)dehydroalanine Methyl Esters and Their Application as Building Blocks in the Syntheses of Amino AcidsStarting with serine, the useful N-(arylmethylene)dehydroalanine methyl esters 6 have been synthesized. These compounds react with nucleophiles in a Michael fashion to give the amino acid derivatives 8 and 9. - Hence, the Michael addition of diorganocopper(I) reagents as C nucleophiles to 6a yielding 9 provides a new method of amino acid synthesis. The extent of the desired 1,4 addition varies with the nature of the reagent and is dependent on several experimental parameters, viz: type of Cu(I) salt, complexing ligands, solvent, and temperature.
    Notes: Ausgehend von Serin wurden die vielseitig einsetzbaren N-(Arylmethylen)dehydroalanin-methylester 6 dargestellt. Diese reagieren mit Nucleophilen im Sinne einer Michael-Addition, wobei die Aminosäurederivate 8 und 9 entstehen. - Die Addition von Diorganokupfer(I)-Reagenzien als C-Nucleophile an 6a zu 9 bietet einen Weg zur Aminosäuresynthese. Das Ausmaß an gewünschter 1,4-Addition ändert sich mit der Natur der Addenden und ist von einer Reihe experimenteller Parameter abhängig, wie etwa der Art des Cu(I)-Salzes, der Anwesenheit komplexierender Liganden, dem Lösungsmittel sowie der Temperatur.
    Additional Material: 1 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1988 (1988), S. 1073-1078 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Building Units of Oligosaccharides, XCI. - Synthesis of Disaccharides from L-glycero-D-manno-Heptose and 2-Amino-2-deoxy-D-glucoseCoupling of 3,4,6-tri-O-acetyl-2-azido-2-deoxy-α-D-glucopyranosyl bromide (9) with benzyl 2,3,5,6-tetra-O-benzyl-L-glycero-α-D-manno-heptofuranoside (10) gives in the presence of silver triflate stereoselectively the α-glycoside 12, in the presence of silver silicate the β-glycoside 14. Removal of protecting groups of 12 leads to α-D-GlcpN-(1→7)-LD-Hepp (20), a partial structure of the core of Aeromonas hydrophila and Bordetella pertussis LPS. β-D-GlcpN(1→7)-LD-Hepp (21), a core structure of Vibrio ordalii LPS, is obtained after deblocking of 14.
    Notes: Die Umsetzung von 3,4,6-Tri-O-acetyl-2-azido-2-desoxy-α-D-glucopyranosylbromid (9) mit Benzyl-2,3,5,6-tetra-O-benzyl-L-glycero-α-Dmanno-heptofuranosid (10) ergibt bei Gegenwart von Silbertriflat stereoselektiv das α-glycosidisch verknüpfte Disaccharid 12, bei Gegenwart von Silbersilicat dagegen stereoselektiv das β-glycosidisch verknüpfte Disaccharid 14. Aus 12 ist durch Entblockierung α-D-GlcpN-(1→7)-LD-Hepp (20), ein Element der Core-Struktur des LPS von Aeromonas hydrophila und Bordetella pertussis, zugänglich. Aus 14 wird durch Entblockierung die Struktur β-D-GlcpN-(1→7)-LD-Hepp (21) aus Vibrio ordalii erhalten.
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