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 mild and efficient synthesis of chiral tetrahydroquinolino pyranose derivatives catalyzed by lanthanum(iii) nitrate hexahydrate

Abstract: A mild and highly efficient synthesis of chiral tetrahydroquinolino pyranose derivatives is described. The reaction of a chiral α,β-unsaturated aldehyde containing a hydroxyl group with different aryl amines using lanthanum(III) nitrate hexahydrate as a catalyst afforded corresponding chiral tetrahydroquinolinated pyranosides in excellent yields. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:429–433, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20441

Studies of Carbohydrate Derivatives by Nuclear Magnetic Double Resonance. Part VI. The Identification of 13C Chemical Shifts of Methyl Resonances via the 1H–{13C} INDOR Technique

Abstract: The 13C chemical shifts of acetate- and methoxyl-methyl substituents of several pyranose carbohydrate derivatives have been measured by the 1H–{13C} INDOR technique. The chemical shifts (δ13C) of anomeric methoxyl-methyl resonances fall into two groups: for α-anomers (axial substituent), δ13C = 55.12–56.63 p.p.m.; for β-anomers (equatorial substituent), δ13C = 56.63–8.69 p.p.m. O-Acetyl-methyl shifts fall between 20.54–20.72 p.p.m. and N-acetyl-methyl shifts were detected between 22.98–23.08 p.p.m.

Formation of glycosides by epoxidation-ring closure of open-chain hydroxyenol ethers obtained from sugars

Abstract: Z- and E-Hydroxyenol ethers, obtained from aldopentoses by a Horner–Wittig reaction, have been epoxidized using m-chloroperbenzoic acid or t-butyl hydroperoxide. A spontaneous intramolecular cyclization of the intermediate epoxides due to the free hydroxy group present in the starting enol ethers occurs, giving 1,2-trans-glycopyranosides from E-enol ethers. From Z-enol ethers, 1,2-cis-glycopyranosides are obtained, although in the case of complex aglycones the cyclization is not entirely stereospecific. The stereochemical course of both the epoxidation reaction and the pyranose ring formation from the intermediate epoxides is discussed.

Synergistic contributions of asparagine 46 and aspartate 52 to the catalytic mechanism of chicken egg white lysozyme

Abstract: The X-ray structure of a chicken egg white lysozyme (ChEWL) complex with a peptidoglycan-derived inhibitor suggests that interactions of Asn46 and Asp52 with the D-subsite N-acetylmuramic acid residue help to distort that pyranose ring into the reactive half-chair conformation and that a hydrogen bond is formed between Asn46 and Asp52 [Strynadka, N. C. J., & James, M. N. G. (1991) J. Mol. Biol. 220, 401-424]. These hypotheses were investigated through the D52A, N46A, and D52A/N46A mutants of ChEWL. The Michaelis constants of the D52A and D52A/N46A ChEWL complexes with Micrococcus luteus cells are 3- and 4-fold higher, respectively, than the wild-type KM; the corresponding kcat values are 25- and 50-fold lower, respectively, than the wild-type kcat. These results support the proposal of Strynadka and James. The velocities of reactions catalyzed by the N46A and D52A mutants are approximately equal to each other for all classes of substrate, suggesting that the respective roles of Asn46 and Asp52 in transition state stabilization do not vary. The mutation of either Asn46 or Asp52 to Ala apparently disrupts the interactions of the other (nonmutated) residue with the substrate, supporting the crystallographic evidence of a hydrogen-bond interaction between the two residues. The mutations do not change the values of the dissociation constants of complexes with (carboxymethyl)chitin complexes, suggesting that ground state complexes of ChEWL with chitin-derived substrates differ in conformation from complexes with bacterial peptidoglycans.