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  • 1
    Electronic Resource
    Electronic Resource
    Glycosylimidate, 25. Muraminsäure als Glycosyldonor und -akzeptor (1987)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 407-415 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Glycosyl Imidates, 25. - Muramic Acid as Glycosyl Donor and Glycosyl AcceptorFrom the 3-O-unprotected 2-azido-2-deoxy-D-glucose derivatives 3 und 4 and trifluoromethanesulfonates of (S)-lactate as alkylating agents the muramic acid derivatives 8a-10a were obtained diastereospecifically and in high yields. (S)-2-Chloropropionates afforded mixtures of diastereoisomers in this reaction. The muramic acid derivatives 8a-10a were readily transformed into glycosyl donors and glycosyl acceptors. Deacetalation of compounds 8a and 10a and subsequent selective 6-O-silylation afforded the glycosyl acceptor 11; reaction with α-trichloroacetimidate 14 as glycosyl donor provided the β-connected disaccharide 15-β. Deprotection yielded the disaccharide 19, the basic unit of the cell wall peptidoglycan of bacteria. Selective desilylation of the muramic acid derivative 8a and formation of the α-trichloroacetimidate 28-α provided a good muramic acid glycosyl donor. With various glycosyl acceptors depending on the catalyst and the reaction conditions either β- or α-glycosides and -disaccharides were obtained selectively and in high yields.
    Notes: Aus den 3-O-ungeschützten 2-Azido-2-desoxy-D-glucose-Derivaten 3 und 4 und Trifluormethansulfonaten von (S)-Milchsäureestern als Alkylierungsmittel konnten diastereospezifisch und in hohen Ausbeuten die Muraminsäurederivate 8a-10a erhalten werden. (S)-2-Chlorpropionsäureester lieferte in dieser Reaktion Diastereomere. Die Muraminsäurederivate 8a-10a können in Glycosylakzeptoren und Glycosyldonoren übergeführt werden. So wurde aus 8a und 10a durch Entacetalisierung und selektive 6-O-Silylierung das Muraminsäurederivat 11 als Akzeptor erhalten, der mit dem α-Trichloracetimidat 14 als Donor das β-verknüpfte Disaccharid 15-β lieferte. Schutzgruppenabspaltung führte zur Disaccharid-Grundeinheit 19 des Zellwand-Peptidoglycans von Bakterien. Selektive 1-Entsilylierung des Muraminsäurederivates 8a und Bildung des α-Trichloracetimidats 28-α ergab einen Muraminsäure-Glycosyldonor. Mit verschiedenen Akzeptoren wurden in Abhängigkeit vom Katalysator und von den Reaktionsbedingungen selektiv und in hohen Ausbeuten β- oder α-Glycoside und -Disaccharide synthetisiert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198719870345
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  • 2
    Electronic Resource
    Electronic Resource
    Glycosylimidate, 16. Synthese des Trisaccharids aus der „Repeating Unit“ des Kapselpolysaccharids von Neisseria meningitidis (Serogruppe L) (1985)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1985 (1985), S. 1537-1545 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Glycosyl Imidates, 161).- Synthesis of the Trisaccharide of the Repeating Unit of the Capsular Polysaccharide of Neisseria meningitidis (Serogroup L)D-Glucal was transformed into the O-benzyl-protected O-(2-azido-2-deoxy-α-D-glucopyranosyl)trichloroacetimidate 5 suitable as glucosyl donor. Compound 5 yielded with 3-O-unprotected 2-azido-2-deoxy-D-glucose derivative 12 as acceptor, also obtained from D-glucal, under Et2O- BF3 catalysis exclusively the β-(1 → 3) linked disaccharide 13. Compound 13 was transformed into the disaccharide donor α-trichloroacetimidate 15 which yielded with compound 12 as acceptor β-specifically the trisaccharide 16. Removal of the 1-O-silyl protective group, reduction of the azido groups, hydrogenolytic debenzylation, and peracetylation gave the per-O-acetylated trisaccharide β-D-GlcNAc-(1 → 3)-β-D-GlcNAc-(1 → 3)-β-D-GlcNAc from the repeating unit of the capsular polysaccharide of Neisseria meningitidis (Serogroup L).
    Notes: Aus D-Glucal wurde das O-benzylgeschützte O-(2-Azido-2-desoxy-α-D-glucopyranosyl)trichloracetimidat 5 als Glucosyldonor synthetisiert, das mit dem aus D-Glucal erhaltenen 3-O-ungeschützten 2-Azido-2-desoxy-D-glucose-Derivat 12 als Akzeptor unter Et2O- BF3-Katalyse ausschließlich das β-(1 → 3)-verknüpfte Disaccharid 13 lieferte. Überführung in das α-Trichloracetimidat 15 als Disaccharid-Donor führte dann mit dem Glycosylakzeptor 12 ebenfalls β-spezifisch zum Trisaccharid 16. Abspaltung der 1-O-Silylschutzgruppe, Reduktion der Azidgruppen, hydrogenolytische Debenzylierung und Peracetylierung lieferte das per-O-acetylierte Trisaccharid β-D-GlcNAc-(1 → 3)-β-D-GlcNAc-(1 → 3)-β-D-GlcNAc aus der „Repeating Unit“ des Kapselpolysaccharids von Neisseria meningitidis (Serogruppe L).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198519850803
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  • 3
    Electronic Resource
    Electronic Resource
    Glycosyl imidates. 49. Synthesis of the octasaccharide moiety of the dimeric Lex antigen (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 425-433 
    Details
    ISSN: 0170-2041
    Keywords: Lewis antigen X ; O-Glycosyl trichloroacetimidates ; Glycosylation procedure, inverted ; O-Protection, selective ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A versatile synthesis of the basic Galβ (1→4)[Fucα(1→3)]-GlcNAc trisaccharide building block of the Lex antigen family based on two important findings could be developed. Firstly, selective 3-O-allylation of the readily available azidolactose derivative 3 led to an efficient synthesis of the 3-O-unprotected fucosyl acceptor 9. Secondly, α-fucosylation of 9 with O-fucosyl trichloroacetimidate 11 as donor exhibited a dramatic increase in yield when carried out by an “inverted procedure”, i,e, the donor was added to an acceptor/catalyst solution. The obtained trisaccharide building block 12 could be readily transformed into acceptor 13 and donor 15, respectively. Thus, the dimeric hexasaccharide 16 was obtained, which was then transformed into donor 19. Its reaction with the 3′-O-unprotected lactose acceptor 20 provided the desired ocetasaccharide 21, which gave upon azido group reduction, acetylation of the amino groups, and complete O-deprotection the desired target molecule 2 characterized as its fully O-acetylated product 24.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199119910178
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  • 4
    Electronic Resource
    Electronic Resource
    Tumor-associated antigen synthesis synthesis of the gal-α-(1→3)-gal-β-(1→4)-GlcNAc epitope a specific determinant for metastatic progression? (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 607-614 
    Details
    ISSN: 0170-2041
    Keywords: Tumor-associated antigens ; Carbohydrates ; Glycosyl trichloroacetimidates ; Trichloroacetimidates ; Alkylation, selective ; Hapten synthesis ; Antigens ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A versatile synthesis of the Gal-α-(1→3)-Gal-β-(1→4)-GlcNAc epitope coupled to an alkyl spacer molecule could be developed. The important building block 3′-allyl-D-lactal 6 was prepared in high yield by the action of dibutyltin oxide and allyl bromide on D-lactal and converted in several steps into the lactosamine derivative 13 with free 3′-OH group. Stereoselective glycosidation with the β-trichloroacetimidate of benzylated D-galactose 18 led to the trisaccharide in high yield. Activation of the protected Gal-α-(1→3)-Gal-β-(1→4)-GlcNAc derivative 21 by desilylation and trichloroacetimidate formation followed by glycosidation with ethyl 9-hydroxynonanoate furnished the spacer-bound trisaccharide hapten 24 in excellent yield after simple two-step deprotection. The trisaccharide hapten 24 can easily be used as immunogen after coupling to an immunogenic carrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1991199101113
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