Topic
Pyranose
About: Pyranose is a research topic. Over the lifetime, 1619 publications have been published within this topic receiving 35348 citations. The topic is also known as: pyranoses & hexopyranose.
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TL;DR: The results strongly suggest that stereocontrol of the cyclization is dependent on conformational and stereoelectronic factors and further oxidative opening of the 1-hydroxy-1-methyl-2-cyclobutanone moiety affords new C-ketoside derivatives either in C- and O-glycoside series.
Abstract: Photolysis of 1-glycosyl-2,3-butanodione derivatives using visible light is a mild and selective procedure for the synthesis of chiral 1-hydroxy-1-methyl-5-oxaspiro[3.5]nonan-2-one carbohydrate derivatives. The results strongly suggest that stereocontrol of the cyclization is dependent on conformational and stereoelectronic factors. Further oxidative opening of the 1-hydroxy-1-methyl-2-cyclobutanone moiety affords new C-ketoside derivatives either in C- and O-glycoside series. This tandem two-step process could be considered to be a stereocontrolled 1,3-transference of an acetyl group, and it can be applied either to pyranose and furanose models.
73 citations
TL;DR: In order to overcome the difficulties in analyzing the NOE data due to the two sets of proton overlaps, molecular modeling of alpha-2,8-linked sialic acid oligomers was carried out to investigate possible conformers, and theoretical NOE calculations were performed by using CORMA (complete relaxation matrix analysis).
Abstract: The solution conformations of the group B polysaccharide of Neisseria meningitidis were analyzed by DQF-COSY and pure absorption 2D NOE NMR with three mixing times. The pyranose ring of the sialic acid residue was found to be in the 2C5 conformation. The DQF-COSY analysis indicated that the orientations of H6 and H7 and of H7 and H8 are both gauche. In order to overcome the difficulties in analyzing the NOE data due to the two sets of proton overlaps, molecular modeling of alpha-2,8-linked sialic acid oligomers was carried out to investigate possible conformers, and theoretical NOE calculations were performed by using CORMA (complete relaxation matrix analysis). Our analysis suggests that the polysaccharide adopts helical structures for which the phi (defined by O6-C2-O8-C8) and psi (C2-O8-C8-C7) angles are in the following ranges: phi -60 to 0 degrees, psi 115-175 degrees or phi 90-120 degrees, psi 55-175 degrees. The weak affinity of anti-B antibodies for smaller alpha-2,8-linked oligosaccharides may be due to the fact that such oligomers are more flexible and may not form an ordered structure as the poly(sialic acid) does.
72 citations
TL;DR: This chapter discusses assay method and purification procedure of the enzyme, and the properties of the isolated glucose 2-oxidase, which appears to play an important metabolic role in basidiomycetes.
Abstract: Publisher Summary Enzymes with glucose 2-oxidase activity, tentatively assigned as pyranose 2-oxidase have so far been isolated from mycelia cultures of two basidiomycetes, Polyporus obtusus and Trametes versicolor . The enzyme is also present in extracts of a number of other higher fungi and appears to play an important metabolic role. This chapter discusses assay method and purification procedure of the enzyme. Glucose 2-oxidase activity is measured using a modification of the chromogenic assay for peroxidase. The chapter also discusses the properties of the isolated glucose 2-oxidase. The purified enzyme has a specific activity of 15.5 U/mg proteins. It is stable at 4° in 30 mM sodium phosphate buffer, pH 6.5 and has a broad pH optimum with maximum activity at pH 7.5. The oxidized form of the enzyme exhibits absorption maxima at 360 and 457 nm. Reduction of the enzyme by the substrate glucose under nitrogen atmosphere, or by sodium dithionite, results in elimination of the absorption maximum at 457 nm. These spectral properties are characteristic of a flavoprotein.
72 citations
TL;DR: The acid degradation of the aldopentoses to furfural and the degradation offurfural were followed spectrophotometrically and are first-order functions of HCI and pentose concentration and are consistent with a positive entropic effect which implies that the transition state involves ring opening.
71 citations