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.

Conformation‐Determining role for the N‐acetyl group in the O‐glycosidic linkage, α‐GalNAc‐Thr

Abstract: An 1H-nmr study of 2-acetamido-2-deoxy-3,4,6-tri-O-acetyl-D-galactopyranose (AcGalNAc) glycosylated Thr-containing tripeptides in Me2SO-d6 solution reveals two mutually exclusive intramolecular hydrogen bonds. In Z-Thr(AcGalNAc)-Ala-Ala-OMe, there is an intramolecular hydrogen bond between the Thr amide proton and the sugar N-acetyl carbonyl oxygen. The strength of this hydrogen bond will be dependent on the amino acid residues on the Thr C terminal side to some undetermined distance. In Ac-Thr(AcGalNAc)-Ala-Ala-OMe, a different intramolecular hydrogen bond between the sugar N-acetyl amide proton and the Thr carbonyl oxygen exists. The choice of hydrogen bonds seems dependent on the bulkiness of the residues on the Thr N terminal side. The consequence of such strong hydrogen bonds is a clearly defined orientation of the sugar moiety with respect to the peptide backbone. In the former, the plane of the sugar pyranose ring is roughly oriented perpendicularly to the peptide backbone. The latter orientation is where the plane of the sugar ring is roughly in line with the peptide backbone. In both orientations, the sugar moiety can increase the shielding of the neighboring amino acid residues from the solvent. The idea that the amino acid residues near the glycosylated Thr influence orientation of the sugar moiety with respect to the peptide backbone and in turn possibly hinder peptide backbone flexibility has interesting implications in the conformational as well as the biological role of O-glycoproteins.

Synthesis of a novel N-selective ester functionalized chitin derivative and water-soluble carboxyethylchitin

Abstract: A novel chitin detivative having a pendant ester function, 2-N-(2-ethoxycarbonylmethyl)chain (2), was synthesized by a Michael-type nucleophilic addition of an amino group of partially deacetylated chitin (1) to ethyl acrylate in phosphate buffer/methanol (5:3, v/v) at 40°C. N-Selective monosubstitution occurred exclusively in the polymer reaction, which was supported by a reaction of methyl 2-ammo-2-deoxy-D-glucopycanoside with ethyl acrylate to afford methyl 2-N-(2-ethexycarbonylethyl)-2-amino-2-deoxy-D-glucopyranoside. The degrees of substitution (DSs) of 2 were determined by 1 H NMR spectroscopy. T1 analysis of 2 was carried out in other to clarify differences of signal intensities of the pendant ester protons and the pyranose ring pronons. The result of the T 1 measurement suggested a relatively restricted molecular motion of the chitin backbone in comparison with the flexible pendant ethyl ester groups. Furthermore, 2-N-(2-carboxyethyl)chitin sodium salt (3) was synthesized from ethyl aorylate and 1 by the Michael addition followed by hydrolysis in 0,1 N NaOH aq, as 40°C, The DSs of 3 were varied from 0.26 to 0.88, which were almost controlled by the reaction period of the Michael reaction from 6 to 168 h. 3 showed good solubility in water. Viscosity measured on a cone-plate viscometer for the 1.0 wt.-% aqueous solution of 3 (DS, 0,26) was 0.074 Pas.sec.