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  • 1
    Electronic Resource
    Electronic Resource
    Structural variations of N-acetylneuraminic acid, part 19: Synthesis of both epimeric pairs of the 4-C-methyl- and 4-deoxy-4-C-methyl- as well as of the β-methylketoside of 4-deoxy-4-C-methylene-N-acetylneuraminic acid (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 111-125 
    Details
    ISSN: 1434-4475
    Keywords: Sialic acids ; Methyl-branched sugars ; Zirconium organyls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Während die Umsetzung des 4-Oxoderivates2 a mit (BuO)3 MeZr ausschließlich zur equatorialen 4-C-Methylverbindung3 a führt, wurde bei der Reaktion mitMe 4Zr ein 3:2-Gemisch der beiden Diastereomeren3 a und4 a erhalten. Das 4-C-Methylenderivat7 a wurde durch Reaktion derselben 4-Oxoverbindung mit CH2I2/Zn/Cp 2ZrCl2 erhalten. Eine anschließende Hydrierung (H2-Pd/C) führte zu einem trennbaren Germisch der beiden 4-Deoxy-4-C-methylderivative8 a und9 a. Diese Verbindungen konnten durch das Entfernen der Schutzgruppen einerseits in die 5-Acetamido-3,4,5-trideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonsäure10 a und 5-Acetamido-2,7-anhydro-4-C-methyl-3,4,5-tridoxy-D-glycero-D-talo-2-nonulosonsäure11 a umgewandelt werden. Die Verbindungen Methyl-5-acetamido-4-C-methylen-3,4,5-trideoxy-β-D-manno-2-nonulopyranosidonat (15) und Methyl-5-acetemido-4-C-methyl-3,4,5-tridoxy-β-D-glycero-D-talo-2-nonulopyranosidonat (16) wurden als Modellverbindungen für enzymatische Untersuchungen über peracetylierte Zwischenstufen hergestellt. Überraschenderweise zeigte nur die 4-C-Methylenverbindung15 eine starke kompetitive Hemmung gegenüber CMP-Sialat-Synthase.
    Notes: Summary While the reaction of the 4-oxo-Neu 5 Ac derivative2 a with tributoxy methyl zirconate led exclusively to equatorial 4-C-methyl derivative3 a, the analogous reaction with tetramethyl zirconate yielded a 3:2 mixture of both diastereoisomeres3 a and4 a. After removal of protecting groups the 5-acetamido-3,4-dideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonic acid5 a and 5-acetamido-3,4-dideoxy-4-C-methyl-D-glycero-D-talo-2-nonulosonic acid6 a were obtained. The 4-C-methylene derivative was prepared by treatment of the same 4-oxo-derivative with CH2I2/Zn/Cp 2ZrCl2. Subsequent hydrogenation led to both epimeric 4-deoxy-4-C-methyl derivatives8 a and9 a. Final removal of protecting groups gave the 5-acetamido-3,4,5-trideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonic acid10 a respectively the 5-acetamido-2,7-anhydro-4-C-methyl-3,4,5-trideoxy-D-glycero-D-talo-2-nonulosonic acid11 a. The β-methylketosides of the 4-deoxy-4-C-methyl- (16) and 4-C-methylene-Neu 5 Ac (15) were prepared via the peracetylated derivatives to obtain modell substrates for enzymatic studies. Thus all free acids were tested for inhibition of CMP-sialate synthease. Only the 4-C-methylene compound15 showed most unexpectedly a strong competitive inhibition of this enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00815172
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  • 2
    Electronic Resource
    Electronic Resource
    Structural variations of N-acetylneuraminic acid, 24: Synthesis of the α-methylketoside of 8-oxo-N-acetylneuraminic acid and related derivatives (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 995-1003 
    Details
    ISSN: 1434-4475
    Keywords: Sialic acids ; Keto-sugars ; Synthesis of a methyl glycoside
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird ein Zugang zu Natrium-(5-acetamido-2,3,5-trideoxy-2,3-didehydro-D-galacto-2,8-nondiulopyranosid)onat-8,8-dimethylacetal (8), Methyl-5-acetamido-3,5-dideoxy-α-D-galacto-2,8-nondiulopyranosidonat-8,8-dimethyl acetal (11) und Methyl-5-acetamido-3,5-dideoxy-α-D-galacto-2,8-nondiulopyranosidonsäure (12) über ein gemeinsames, leicht herzustellendes 8-Oxo-Sialinsäurederivat5 beschrieben. Die glycosidische Bindung der Verbindungen11 bzw.12 zeigt eine bemerkenswerte Stabilität gegenüber sauren Reaktionbedingungen, welche im Gegensatz zu Beobachtungen an anderen Neuraminsäuremethylketosiden steht.
    Notes: Abstract The synthesis of the sodium 5-acetamido-2,3,5-trideoxy-2,3 didehydro-D-galacto-2,8-nondiulopyranosidonate 8,8-dimethyl acetal (8) and of the methyl-5-acetamido-3,5-dideoxy-α-D-galacto-2,8-nondiulopyranosidonate 8,8 dimethyl acetal (11) as well as of the methyl-5-acetamido-3,5-dideoxy-α-D-galacto-2,8-nondiulopyranosidonic acid (12) is reported involving the easily accessible 8-oxoderivative5. Compounds11 and12, respectively, showed to have glycosidic bond with remarkable stability to acidic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00823430
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  • 3
    Electronic Resource
    Electronic Resource
    Structural variations of N-Acetylneuraminic acid, 12: A new useful approach to 4-epi- and 8-epi-N-Acetylneuraminic acid (1989)
    Springer
    Monatshefte für Chemie 120 (1989), S. 899-906 
    Details
    ISSN: 1434-4475
    Keywords: Borane-ammonia complex ; Ruthenium tetroxide ; Sialic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die leicht zugänglichen Neuraminsäurederivate1 und7 werden mittels RuO4 in die Ketone2 und8 umgewandelt, welche mit dem Ammoniak-Boran-Komplex diastereoselektiv zu den entsprechenden 4- und 8-Epimeren4 a und10 reduziert werden. Anschließende Deblockierungsschritte führen zu den Titelverbindungen5 und12. Diese Synthesewege sind für den Grammaßstab ausgearbeitet worden.
    Notes: Summary Readily available Neu5Ac derivatives1 and7 are oxidized by RuO4 to the ketones2 and8 which are reduced diastereoselectively by the borane-ammonia complex to yield the4- and 8-epimers4a and10. Subsequent deprotection leads to the title compounds5 and12. This few step procedure is also applicable on gram scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811129
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  • 4
    Electronic Resource
    Electronic Resource
    Structural variations of N-acetylneuraminic acid, 14. Synthesis of the β-methyl ketosides of 4-oxo-, 7-oxo-, and 8-oxo-N-acetylneuraminic acid and the corresponding 7,7- and 8,8-dimethoxy derivatives their behaviour towards CMP-sialate synthase (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 83-91 
    Details
    ISSN: 0170-2041
    Keywords: CMP-sialate synthase ; Sialic acids ; N-Acetylneuraminic acid derivatives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 4-, 7-, and 8-oxo-sialic acid β-methyl ketosides 7, 10a, and 11a were obtained by transformation of easily available derivatives of N-acetylneuraminic acid (1a). The carbonyl migration from C-7 to C-8 can be carried out under well-defined conditions with formation of the ketone 11b. Starting from 7- and 8-ketones 17 and 20 the corresponding dimethyl acetals are prepared. The 4-ketone 7 behaves as a moderate competitive inhibitor of CMP-sialate synthase [EC 2.7.7.43], whereas the 8-ketone 11a, the 8,8-dimethyl acetal 19, and the 7,7-dimethyl acetal 23 prove not to be inhibitors of this enzyme. The 7-ketone 10a was not tested because of instability under test conditions at pH 8.5.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199019900112
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  • 5
    Electronic Resource
    Electronic Resource
    Structural variations of N-acetylneuraminic acid, 18. Synthesis of the side chain stereo and deoxy analogs of 5-acetamido-2,6-anhydro-3,5-dideoxy-D-erythro-L-manno-nononic acid (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 1185-1195 
    Details
    ISSN: 0170-2041
    Keywords: Sialic acids ; Hemagglutinin inhibitors ; N-Acetylneuraminic acid, deoxygenation and epimerization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 5-acetamido-2,6-anhydro-3,5-dideoxy-D- erythro-L-manno-nonic acid (3b, 7,8-epi2-2-d-2-HeqNeu5Ac) and sodium 5-acetamido-2,6-anhydro-3,5-dideoxy-L-threo-L-manno-nonate (6b, 8-epi-2-d-2-Heq-Neu5Ac) could be realized by transformation of 5-acetamido-3,5-dideoxy-L-glycero-L-altro-2-nonulopyranosonic acid (2a, 7,8-bis-epi-Neu5Ac) and 5-acetamido-3,5-dideoxy-3-L-glycero-D-galacto-2-nonulosonic acid (5a, 8-epi-Neu5Ac) into the corresponding peracetylated 2-chloro derivatives and subsequent catalytic hydrogenation. As this procedure could not be applied to the synthesis of the 7-epi, 7-deoxy and 8-deoxy derivatives a new strategy, which started with the methyl 5-acetamido-2,6-anhydro-3,5-dideoxy-D-erythro-L-manno-nonoate (1e), was designed. For this purpose, a gram-scale preparation of 1e was developed. Transformation of protecting groups and radical reduction of selectively introduced tolylthiocarbonate groups led to the corresponding 5-acetamido-2,6-anhydro-3,5,7-trideoxy-D-glycero-L-manno-nonoic acid (12b, 2,7-d2-2Heq-Neu5Ac) and sodium 5-acetamido-2,6-anhydro-3,5,8-trideoxy-D-glycero-L-manno-nonate (11b, 2,8-d2-2Heq-Neu5Ac). An oxidation  -  reduction sequence yielded 5-acetamido-2,6-anhydro-3,5-dideoxy-D-threo-L-manno-nonoic acid (9c, 2d-2Heq-7-epi-Neu5Ac). Also the sialic acid analog 6b could be prepared according to this newly designed strategy.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1990199001216
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