<b>Rates of Reaction of Nitrogen Bases with Sugars. I. Studies of Aldose Oxime, Semicarbazone and Hydrazone Formation</b>

Haas, John W.; Kadunce, Raymond E.

doi:10.1021/ja00883a056

Cited by 20 publications

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“…Seminal kinetic studies of aldose oxime, hydrazone, and semicarbazone formation by Haas and Kadunce established a common mechanism of this family of reactions, proceeding according to the reaction pathway shown in Scheme , in which the reactive species is the open‐chain aldehydo form. When conducted in aqueous solution, product formation generally proceeds with an optimum at pH 4–5 . The pH optimum reflects a change in rate‐determining step between dehydration of the intermediate carbinolamine at higher pH and nucleophilic attack at lower pH, the p K a values of α‐nucleophiles typically being in this range.…”

Section: Glycosyl Oximes/oxyamines and Hydrazonesmentioning

confidence: 99%

“… Reaction pathway for condensation of three types of α‐nucleophiles (R 1 NH−XR 2 ) with reducing sugars, shown for d ‐glucose …”

Section: Glycosyl Oximes/oxyamines and Hydrazonesmentioning

confidence: 99%

“…Seminal kinetic studies of aldose oxime, hydrazone, and semicarbazone formation by Haas and Kadunce [124] established ac ommon mechanism of this family of reactions, proceeding according to the reactionp athway shown in Scheme 36, in which the reactive species is the open-chain aldehydo form. When conducted in aqueous solution, product formation generally proceeds with an optimum at pH 4-5.…”

Section: Glycosyl Oximes/oxyamines and Hydrazonesmentioning

confidence: 99%

“…When conducted in aqueous solution, product formation generally proceeds with an optimum at pH 4-5. [124] The pH optimum reflects ac hange in rate-determining step between dehydration of the intermediate carbinolamine at higher pH and Scheme34. Oxidationofd-mannose by using Shvo's catalyst.…”

Section: Glycosyl Oximes/oxyamines and Hydrazonesmentioning

confidence: 99%

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Chemoselective Reactions for the Synthesis of Glycoconjugates from Unprotected Carbohydrates

et al. 2017

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Glycobiology is the comprehensive biological investigation of carbohydrates. The study of the role and function of complex carbohydrates often requires the attachment of carbohydrates to surfaces, their tagging with fluorophores, or their conversion into natural or non-natural glycoconjugates, such as glycopeptides or glycolipids. Glycobiology and its "omics", glycomics, require easy and robust chemical methods for the construction of these glycoconjugates. This review gives an overview of the rapidly expanding field of chemical reactions that selectively convert unprotected carbohydrates into glycoconjugates through the anomeric position. The discussion is divided in terms of the anomeric bond type of the newly formed glycoconjugates, including O-, N-, S-, and C-glycosides.

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Section: Glycosyl Oximes/oxyamines and Hydrazonesmentioning

confidence: 99%

“… Reaction pathway for condensation of three types of α‐nucleophiles (R 1 NH−XR 2 ) with reducing sugars, shown for d ‐glucose …”

Section: Glycosyl Oximes/oxyamines and Hydrazonesmentioning

confidence: 99%

Section: Glycosyl Oximes/oxyamines and Hydrazonesmentioning

confidence: 99%

Section: Glycosyl Oximes/oxyamines and Hydrazonesmentioning

confidence: 99%

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Chemoselective Reactions for the Synthesis of Glycoconjugates from Unprotected Carbohydrates

et al. 2017

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“…[32] The equilibrium constants for such kind of condensations are moderate, [31,32] and high yields are often obtained by performing the reactions under concentrated conditions. However, this cannot be used for complex glycans derived from natural sources, as they are difficult and expensive to isolate in large amounts.…”

Section: Preparation Of Glycan-liker Conjugates For Microarray Fabricmentioning

confidence: 99%

Chemoselective Reagents for Covalent Capture and Display of Glycans in Microarrays

2010

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Glycobiology has made very significant progress in the past decades. However, further progress will significantly depend on the establishment of novel methods for miniaturized, high‐throughput analysis of glycan–protein interactions. Robust solid‐phase chemical tools and new, chemoselective reagents for biologically meaningful display of surface‐immobilized glycans are likely to play a key role. Here we present four new bifunctional linkers that allow highly chemoselective capture of unprotected glycans in solution to form glycan‐linker conjugates for direct construction of glycan microarrays (glycochips). The bifunctional linkers carry O‐linked aminooxy moieties, some with N‐substituents at one end and an amino group at the other. In addition, they contain a substituted benzene ring for UV traceability and improved purification of glycan‐linker conjugates. NMR spectroscopic studies in solution proved that N‐substituted aminooxy linkers provided model glycan‐linker conjugates with the β‐glucopyranoside configuration, i.e. the ring‐closed form required for biological recognition. Then an ensemble of glycan‐linker conjugates were assembled from mannobiose, lactose, and N‐acetyl‐lactosamine and used for covalent printing of glycan microarrays. The stability of oximes were studied both in solution and on‐chip. In solution, two of the linkers provided glycan‐linker conjugates with a remarkable stability at pH 4 or higher, on‐chip this relative stability was upheld. Two of the linkers, with different properties, are recommended for the glycobiology toolbox for the construction of glycan microarrays from unprotected glycans.

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Glycosylhydrazine, 2. Aufbauende Synthese von Pyrazolnucleosiden über Ribosylhydrazine

1977

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Das ringoffene D-Ribosehydrazon 5, das mit den ringgeschlossenen Ribosylhydrazinen 3, 4, 7 und 8 im Gleichgewicht steht, bildet mit f3-Dicarbonylverbindungen keine Pyrazolnucleoside. Die hier verfolgte aufbauende Synthesemethode zur Herstellung von Nucieosiden gelingt jedoch dann, wenn die freien Hydroxygruppen teilweise oder ganz mit Schutzgruppen versehen werden.Die d a m hergestellten D-Ribosehydrazon-Derivate 13af stehen mit den entsprechenden Ribofuranosylhydrazinen 12 und 14 im Gleichgewicht. Sie liefern mit 8-Dicarbonylverbindungen je nach Raumerfullung und Position der Schutzgruppen ein Gemisch aus a-und 0-Pyrazoinucleosiden (24 bzw. 18 -21) oder ausschlieDlich das P-Anomere, d. h., in einem Reaktionsschritt werden zwei Ringe und ein Chiralitatszentrum selektiv gebildet.Glycosylhydrazines, 2 Synthesis of Pyrazole Nucleosides via RibosylhydrazinesThe open-chain D-ribose hydrazone 5, which is in equilibrium with the closed-ring ribosylhydrazines 3,4,7, and 8, forms no pyrazole nucleosides with P-dicarbonyl compounds. However this method for the synthesis of nucleosides is successful if protective groups are attached to part or all of the free hydroxylic groups. The synthesized D-ribose hydrazone derivatives 13af are in equilibrium with the corresponding ribofuranosylhydrazines 12 and 14. According to size and position of the protective groups they react with 8-dicarbonyl compounds to yield either a mixture of a-and P-pyrazole nucleosides (24 or 18-21) or only the p-anomer. Thus in one reaction step two rings and one chiral center are created selectively.Allopurinolribosid 1 und Virazol (2) sind Nucleoside, die vermutlich pharmazeutische Bedeutung haben. Allopurinol hemmt die Xanthinoxidase; es wird zur Behandlung von Gicht eingesetzt. In vivo wird Allopurinol in das Ribosid 1 umgewandelt, das loslicher und weniger toxisch ist 3-4). Virazol(2), das vor allem von Robins und Mitarbb. untersucht wurde, hat breite antivirale Aktivitat ').

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Rates of Reaction of Nitrogen Bases with Sugars. I. Studies of Aldose Oxime, Semicarbazone and Hydrazone Formation

Cited by 20 publications

References 0 publications

Chemoselective Reactions for the Synthesis of Glycoconjugates from Unprotected Carbohydrates

Chemoselective Reactions for the Synthesis of Glycoconjugates from Unprotected Carbohydrates

Chemoselective Reagents for Covalent Capture and Display of Glycans in Microarrays

Glycosylhydrazine, 2. Aufbauende Synthese von Pyrazolnucleosiden über Ribosylhydrazine

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