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  • 1
    Electronic Resource
    Electronic Resource
    Bausteine von Oligosacchariden, LXVI. Synthese von O-Glycopeptid-Blöcken des Glycophorins (1985)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1985 (1985), S. 2028-2048 
    Details
    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, LXVI.  -  Synthesis of O-Glycopeptide Blocks of GlycophorineA block synthesis to O-glycopeptides can be realized by reaction of the disaccharide halide 10 with either L-serine- or L-threonine-containing peptide derivatives. Thus, the reaction of 10 with 8 yields stereoselectively the L-Ser-L-Ser derivative 15 in which two disaccharide residues are α-glycosidically linked to the peptide. However, this method is limited by the low solubilities of peptide derivatives in dichloromethane. A more general procedure represents the step-by-step synthesis of O-glycopeptides in which selectively deblocked derivatives of disaccharide amino acids are combined by using the methods of peptide syntheses. An example is the reaction of 25 with 29 in the presence of EEDQ yielding the glycopeptide 30. The reagent potassium cyanide in methanol/ethanol proved to be the most suitable deacylation reagent for the deblocking of the saccharide units in the last step. The benzoyl groups can be removed without β-elimination or racemization of the peptide part.
    Notes: Eine Blocksynthese zu O-Glycopeptiden ist durch Umsetzung des Disaccharidhalogenides 10 mit L-Serin- oder L-Threonin-haltigen Peptid-Derivaten möglich. So ergibt die Umsetzung von 10 mit 8 stereoselektiv das L-Ser-L-Ser-Derivat 15, an das α-glycosidisch zwei Disaccharid-Reste geknüpft sind. Diese Methode wird jedoch durch geringe Löslichkeiten von Peptid-Derivaten in Dichlormethan begrenzt. Universeller anwendbar ist eine stufenweise Synthese von O-Glycopeptiden, bei der selektiv entblockierte Derivate von Disaccharid-Aminosäuren nach den Methoden der Peptidchemie verknüpft werden. So ergibt die Reaktion von 25 mit 29 in Gegenwart von EEDQ das Glycopeptid 30. Als bestes Entacylierungs-Reagenz für die Deblockierung der Saccharid-Einheiten im letzten Schritt hat sich Kaliumcyanid/Methanol/Ethanol bewährt. Hiermit erfolgt auch Abspaltung der Benzoylgruppen ohne β-Eliminierung oder Racemisierung des Peptidteiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198519851011
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  • 2
    Electronic Resource
    Electronic Resource
    Bausteine von Oligosacchariden, LXXIII. Synthese der Tetrapeptidsequenz 12 bis 15 des Asialoglycophorin A mit vier Disaccharid-Seitenketten (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1435-1447 
    Details
    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, LXXIII. - Synthesis of the Tetrapeptide Sequence 12 to 15 of Asialoglycophorin A with Four Disaccharide Side ChainsThe protected O-glycosylated derivative of L-serine 2 and the homologous L-threonine compound 8, both with the Fmoc-group at the N-terminus and the benzyl ester at the C-terminus, can be used successfully in the synthesis of O-glycopeptides. In these compounds, it is possible to deblock the N-terminus or the C-terminus selectively. Beginning at the carboxyl end and with help of the peptide reagent EEDQ, these derivatives were used in a step by step synthesis of the glycosylated tetrapeptide 19. This structure with four disaccharide units of β-D-Gal-(1→3)-α-D-GalNAc represents the sequence 12 to 15 of the asialoglycophorin A.
    Notes: Das blockierte O-Glycosylserin-Derivat β-D-Gal-(1→3)-α-D-GalNAc-L-Ser 2 mit N-terminaler Fmoc-Gruppe und C-terminalen Benzylester sowie die entsprechende L-Threonin-verbindung 8 bieten einen allgemeinen Zugang zu O-Glycopeptiden. In ihnen läßt sich selektiv der N- oder C-Terminus freilegen. Beginnend am C-terminalen Ende wurde hiermit stufenweise unter Kondensationshilfe von EEDQ das Tetraglycopeptid 19 mit vier Disaccharideinheiten β-D-Gal-(1→3)-α-D-GalNAc synthetisiert. Es handelt sich hierbei um die Sequenz 12 bis 15 des Asialoglycophorin A.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619860815
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  • 3
    Electronic Resource
    Electronic Resource
    Synthese eines mit D-Glucuronsäure konjugierten Metaboliten von Ciamexon (1989)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 393-395 
    Details
    ISSN: 0170-2041
    Keywords: Glucuronidation ; Invertomers ; Esterase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of a Metabolite of Ciamexon Conjugated with D-Glucuronic AcidReaction of the alcohol 2 with the glucuronic acid derivative 6 in the presence of Ag triflate yields the protected β-D-glucuronide 8 by rearrangement of the orthoester 7. After deacetylation and saponification with pig liver esterase, the deblocked glucuronide 3 can be isolated. Due to the aziridine ring the glucuronic acid derivatives of 2 consist of a mixture of invertomers, as shown by 1H-NMR spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198919890168
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  • 4
    Electronic Resource
    Electronic Resource
    Ungewöhnliche Reaktion zu Glycosylurethanen bei einer Glycopeptidsynthese (1987)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 577-581 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Unusual Reaction to Glycosyl Urethanes During a Synthesis of GlycopeptidesReaction of the disaccharide halide 1 with N-(3,5-dimethoxy-α,α-dimethylbenzyloxycarbonyl)-L-serine benzyl ester (5) unexpectedly yields the glycosyl urethane 10. Glycosidation of 5 predominantly occurs at the urethane oxygen and not at the free hydroxy group of L-serine. During the formation of 10 the β-hydroxy group of serine is converted into a 3,5-dimethoxy-α,α-dimethylbenzyl ether.
    Notes: Die Umsetzung des Disaccharidhalogenids 1 mit N-(3,5-Dimethoxy-α,α-dimethylbenzyloxycarbonyl)-L- serin-benzylester (5) führt unerwartet zum Glycosylurethan 10. Im Derivat 5 wird bevorzugt der Urethansauerstoff und nicht die freie OH-Gruppe des L-Serins glycosidiert. Während der Reaktion zu 10 erfolgt Überführung der β-OH-Gruppe des Serins in einen (3,5-Dimethoxy-α,α-dimethylbenzyl)ether.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198719870703
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  • 5
    Electronic Resource
    Electronic Resource
    Chemoenzymatische „Chiral-Pool“-Synthese von (+)-exo-Brevicomin aus Kohlenhydraten mit Fructose-1,6-diphosphat-Aldolase (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 1019-1024 
    Details
    ISSN: 0170-2041
    Keywords: Fructose 1,6-diphosphate ; (+)-exo-Brevicomin ; Aldol reaction, enzymatic ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemoenzymatic “Chiral-Pool” Synthesis of (+)-exo-Brevicomin from Carbohydrates Using Fructose 1,6-Diphosphate AldolaseFructose-1,6-diphosphate aldolase (EC 4.1.2.13) catalyzes the stereospecific aldol reaction between 1,3-dihydroxyacetone phosphate (4) and 5-oxohexanal (3) or its 5-dithiane-protected analog 8. The products of the aldol reactions are dephosphorylated with acid phosphatase (EC 3.1.3.2). Whereas the aldol adduct of 3 cyclizes spontaneously to give the bicyclic brevicomin precursor 3, the adduct of 8 first has to be deprotected with sulfuryl chloride and wet silica gel. The resulting bicyclic α-hydroxy ketone 3 is reduced with LiAlH4 to form the 1,2-diol 14 which is then deoxygenated to give the vinyl compound 17 by treatment of the corresponding dixanthate 15 with tributyltin hydride or by treatment of the corresponding mesylate 16 with sodium naphthalenide. The olefin 17 is finally converted to (+)-exo-brevicomin (1) by hydrogenation with diimide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1990199001184
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