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.

Enantioselective synthesis of tetrafluorinated ribose and fructose.

Abstract: A perfluoroalkylidene lithium mediated cyclisation approach for the enantioselective synthesis of a tetrafluorinated aldose (ribose) and of a tetrafluorinated ketose (fructose), both in the furanose and in the pyranose form, is described.

Structural analysis of the core region of lipopolysaccharides from Proteus mirabilis serotypes O6, O48 and O57.

Abstract: The structure of lipid A core region of the lipopolysaccharides (LPS) from Proteus mirabilis serotypes O6, O57 and O48 was determined using NMR, MS and chemical analysis of the oligosaccharides, obtained by mild acid hydrolysis, alkaline deacylation, and deamination of LPS: Incomplete substitutions are indicated by bold italic type. All sugars are present in pyranose form, α-Hep is the residue of lglycero-α-dmanno-Hep, α-dd-Hep is the residue of dglycero-α-dmanno-Hep, l-Ara4N is 4-amino-4-deoxy-l-arabinose, Qui4NAlaAla is the residue of 4-N-(l-alanyl-l-alanyl)-4-amino-4,6-dideoxyglucose. All sugars except l-Ara4N have d-configuration. β-GalA* is partially present in the form of amide with 1,4-diaminobutane (putrescine)-HN(CH2)4NH2 or spermidine-HN(CH2)3NH(CH2)4NH2.

A β-Mannanase with a Lysozyme-like Fold and a Novel Molecular Catalytic Mechanism

Abstract: The enzymatic cleavage of β-1,4-mannans is achieved by endo-β-1,4-mannanases, enzymes involved in germination of seeds and microbial hemicellulose degradation, and which have increasing industrial and consumer product applications. β-Mannanases occur in a range of families of the CAZy sequence-based glycoside hydrolase (GH) classification scheme including families 5, 26, and 113. In this work we reveal that β-mannanases of the newly described GH family 134 differ from other mannanase families in both their mechanism and tertiary structure. A representative GH family 134 endo-β-1,4-mannanase from a Streptomyces sp. displays a fold closely related to that of hen egg white lysozyme but acts with inversion of stereochemistry. A Michaelis complex with mannopentaose, and a product complex with mannotriose, reveal ligands with pyranose rings distorted in an unusual inverted chair conformation. Ab initio quantum mechanics/molecular mechanics metadynamics quantified the energetically accessible ring conformations and provided evidence in support of a 1C4 → 3H4‡ → 3S1 conformational itinerary along the reaction coordinate. This work, in concert with that on GH family 124 cellulases, reveals how the lysozyme fold can be co-opted to catalyze the hydrolysis of different polysaccharides in a mechanistically distinct manner.

Proton magnetic resonance spectra of d-glucopyranose polymers

Abstract: The proton magnetic resonance spectra of carbohydrates in deuterium oxide solution were obtained and considered with respect to probable conformation. The anomeric proton signal occurred at lowest field and was easily recognized. In the various glucose derivatives investigated, this signal occurred from 4.62 to 5.25 τ for equatorial protons and from 5.12 to 5.65 τ for axial protons. Within each of these ranges, the chemical shifts varied inversely with the electronegativity at the C1 site, as calculated by the technique of Gordy (1). Variable electronegativity at C1 accounts for the overlap of ranges for equatorial and axial protons, thereby bringing the n.m.r. data into agreement with assignment of the C1 chair form of the pyranose ring to the linear polymers of D-glucopyranose. The orientation of the glucopyranose rings in cyclodextrins is shown to preclude ring current effects, and the up-field chemical shifts of these materials are shown to be consistent with the C1 form.