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.

A synthesis of pseudouridine and of 5-β-D-ribofuranosyluridine

Abstract: 5-Bromo-2,4-di-t-butoxypyrimidine is converted into the pyrimidin-5-yl-lithium and coupled to 2,4:3,5-di-O-benzylideneribose. Mild acid treatment of the intermediate protected 1-pyrimidin-5-ylpentitol affords 5-β-D-ribofuranosyluracil, pseudouridine, with some α-anomer and only traces of the pyranose isomers. Likewise 5-bromo-2′,3′-O-isopropylideneuridine leads to 5-β-D-ribofuranosyluridine (1,5-diribosyluracil).

Konformationsanalyse, VIII. Tri‐axiale Konformation des 1‐(Tri‐O‐acetyl‐α‐D‐xylopyranosyl)‐imidazols im Kristall

Abstract: 1-(Tri-O-acetyl-α-D-xylopyranosyl)imidazol (1) liegt im Kristall auch ohne wesentlichen Beitrag eines inversen anomeren Effektes in der 1C4-Konformation 1b mit drei axialen Acetyl- und aquatorialer Imidazolgruppe vor. Sterische Grunde sollten hierfur bestimmend sein. In Losung liegt der Anteil an 1C4-Konformation 1b zwischen 35 und 85%. Die dreidimensionale Rontgenstrukturanalyse von 1 (Raumgruppe rhombisch P 21212) zeigt, das infolge 1,3-syn-diaxialer Wechselwirkung der 2-OAc-und-4OAc-Gruppe das C4 des Pyranosesessels von 1b abgeflacht ist. Der Imidazolring steht senkrecht zum Pyranosering und senkrecht auf der abgedrehten 2-OAc-Gruppe. Die Methylgruppe der 2-OAc-Gruppe weist eine, die der 3-OAc- und 4-OAc-Gruppe zwei statistisch verteilte Wasserstofflagen auf. Conformation Analysis, VIII. Tria-axial Conformation of 1-(Tri-O-acetyl-α-D-xylopyranosyl)imidazol in Crystal In the crystalline state 1-(tri-O-acetyl-α-D-xylopyranosyl)imidazole (1) adopts the 1C4 conformation 1b with three axial acetoxy groups and one equatorial imidazol group without considerable contribution of an inverse anomeric effect. This is a consequence of predominating steric effects. In solution the amount of 1C4 conformation 1b varies from 35–85%. The three dimensional X-ray structure analysis of 1 (space group rhombic P 21212) shows that owing to a 1,3-syn-diaxial interaction of the 2-OAc and the 4-OAc groups the pyranose chair of 1b is flattened at C4. The plane of the imidazol ring is perpendicular to the pyranose chair and also perpendicular to the turned 2-OAc group. The methyl group of the 2-OAc group exhibits one, those of the 3-OAc and 4-OAc groups exhibit two statistically distributed hydrogen positions.

Nickel(II) Chloride-Mediated Regioselective Benzylation and Benzoylation of Diequatorial Vicinal Diols

Abstract: Ni(II)-chelates of monosaccharide vicinal diols were found to be useful intermediates in regioselective monobenzylation and monobenzoylation. It was observed that the substitution occurs exclusively at the position adjacent to the axially oriented substituent of the pyranose ring, for example, at C-2 of α-D-gluco and at C3 of β-D-galacto.

Evaluation of fluoropyruvate as nucleophile in reactions catalysed by N -acetyl neuraminic acid lyase variants: scope, limitations and stereoselectivity

Abstract: The catalysis of reactions involving fluoropyruvate as donor by N-acetyl neuraminic acid lyase (NAL) variants was investigated. Under kinetic control, the wild-type enzyme catalysed the reaction between fluoropyruvate and N-acetyl mannosamine to give a 90 : 10 ratio of the (3R,4R)- and (3S,4R)-configured products; after extended reaction times, equilibration occurred to give a 30 : 70 mixture of these products. The efficiency and stereoselectivity of reactions of a range of substrates catalysed by the E192N, E192N/T167V/S208V and E192N/T167G NAL variants were also studied. Using fluoropyruvate and (2R,3S)- or (2S,3R)-2,3-dihydroxy-4-oxo-N,N-dipropylbutanamide as substrates, it was possible to obtain three of the four possible diastereomeric products; for each product, the ratio of anomeric and pyranose/furanose forms was determined. The crystal structure of S. aureus NAL in complex with fluoropyruvate was determined, assisting rationalisation of the stereochemical outcome of C–C bond formation.

Synthesis of uridine 5'-(L-arabinofuranosyl pyrophosphate) and the structure of the UDP-L-arabinose formed in plants from UDP- -D-xylopyranose.

Abstract: Uridine 5′-(L-arabinofuranosyl pyrophosphate) and uridine 5′-(β-L-arabinopyranosyl pyrophosphate) have been synthesized chemically and compared with the UDP-L-arabinose formed from UDP-α-D-xylopyranose and UDP-α-D-glucuronic acid by plant particulate fractions. It is concluded that the product of enzymic reaction has a pyranose ring structure.