In the title molecule, C8H15NO6, the pyranose ring adopts the usual 4C1(D) conformation and the N-acetyl group exists in the Z-anti conformation. The orientation of the primary alcohol group is gauche.

Subramanyam Srinivasan

Kuttikode Priya

Duraikkannu Loganathan

Conformations

Crystal orientation

Molecular crystals

Molecular Structure

X ray crystallography

GLUCOPYRANOSE

Polysaccharides

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

β-1- N -Acetamido- D -glucopyranose

Acta Crystallographica Section C: Crystal Structure Communications

The linkage region constituents, 2-deoxy-2-acetamido-β-D-glucopyranose (GlcNAc) and L-asparagine (Asn) are conserved in the N-glycoproteins of all eukaryotes. Elucidation of the structure and conformation of the linkage region of glycoproteins is important to understand the presentation and dynamics of the carbohydrate chain at the protein/cell surface. Earlier crystallographic studies using monosaccharide models and analogs of N-glycoprotein linkage region have shown that the N-glycosidic torsion, N, is more influenced by the structural variation in the sugar part than that of the aglycon moiety. To access the influence of distal sugar as well as interglycosidic linkage (α or β) on the N-glycosidic torsion angles, cellobiosyl and maltosyl alkanamides have been synthesized and structural features of seven of these analogs have been characterized by X-ray crystallography. Comparative analysis of the seven disaccharide analogs with the reported monosaccharide analogs showed that the N value of cellobiosyl analogs deviate ~9 with respect to GlcβNHAc. In the case of maltosyl analogs, deviation is more than 18. These deviations indicate that the N-glycosidic torsion is influenced by addition of distal sugar as well as with respect to inter glycosidic linkage (α or β); it is less influenced by changes occurring at the aglycon. The χ2 value of alkanamide derived from glucose, cellobiose and maltose exhibit a large range of variations (from 1.6 to -109.9). This large span of χ2 value suggests the greater degree of rotational freedom around C1′-C2′ bond which is restricted in GlcNAc alkanamides. The present finding explicitly proved the importance of molecular architecture in the N-glycoproteins linkage region to maintain the linearity, planarity and rigidity. These factors are necessary for N-glycan to serve role in inter- as well as intramolecular carbohydrate-protein interactions. © 2013 Springer Science+Business Media New York.

Glycoconjugate Journal

Effect of distal sugars and interglycosidic linkage on the N-glycoprotein linkage region conformation: Synthesis and X-Ray crystallographic investigation of β-1-N-alkanamide derivatives of cellobiose and maltose as disaccharide analogs of the conserved chitobiosylasparagine linkage

The torsion angle around the N-glycoprotein linkage region (GlcNAc-Asn) is an important factor for presenting sugar on the cell surface which is crucial for many biological processes. Earlier studies using model and analogs showed that this important torsion angle is greatly influenced by substitutions in the sugar part. In the present work, uronic acid alkanamides and triazole derivatives have been designed and synthesized as newer analogs of N-glycoprotein linkage region to understand the influence of the carboxylic group on linkage region torsion as well as on molecular packing. Crystal structure of N-(β-d-galacturonopyranosyl)acetamide is solved with the space group of P22121. Comparison of the torsion angle and molecular packing of this compound with N-(β-d-galactopyranosyl)acetamide showed that changing the C6-hydoxymethyl group to the carboxylic acid group has minimum influence on the N-glycosidic torsion angle, ΦN and significant influence on the molecular packing. © 2013 Elsevier Ltd. All rights reserved.

Carbohydrate Research

Synthesis of N-(β-d-glycuronopyranosyl)alkanamides and 1-(β-d-glycuronopyranosyl)-4-phenyl-[1,2,3]-triazoles as N-glycoprotein linkage region analogs: Examination of the effect of C5 substituent on the N-glycosidic torsion (ΦN) based on X-ray crystallography

N-Glycoprotein linkage region constituents namely 2-deoxy-2-acetamido- β-d-glucopyranose (GlcNAc) and asparagine (Asn) are conserved among all eukaryotes. Earlier crystallographic studies on the linkage region conformation revealed that among all the models and analogs of the N-glycoprotein linkage region, XylβNHAc showed maximum deviation in the φN value as compared to the value reported for the model compound, GlcNAcβNHAc. In order to understand the effect of another pentopyranose, viz., arabinose, on the N-glycosidic torsion angles and molecular assembly, three arabinopyranosyl alkanamides were synthesized and their X-ray crystal structures elucidated. A comparative analysis of the N-glycosidic torsion, φN of the three analogs revealed the greater rotational freedom around the C1-N1 bond as compared to the GlcNAc derivatives. Molecular assembly of propionamido and chloroacetamido derivatives is characterized by the presence of anti-parallel bilayers of the molecules. This unique molecular assembly is hitherto unknown in all other models and analogs of N-glycoprotein linkage region. This study reveals that N-glycosidic torsions are influenced by the glycan as well as molecular packing. © 2013 Elsevier Ltd. All rights reserved.

Synthesis and X-ray crystallographic investigation of N-(α-d- arabinopyranosyl)alkanamides as N-glycoprotein linkage region analogs

N-Glycoprotein linkage region constituents, 2-acetamido-2-deoxy-β-D- glucopyranose (GlcNAc) and asparagine (Asn) are conserved among all the eukaryotes. To gain a better understanding for nature's choice of GlcNAcβAsn as linkage region constituents and inter- and intramolecular carbohydrate-protein interactions, a detailed systemic structural study of the linkage region conformation is essential. Earlier crystallographic studies of several N-(β-glycopyranosyl)alkanamides showed that N-glycosidic torsion, φN, is influenced to a larger extent by structural variation in the sugar part than that of the aglycon moiety. To explore the effect of the bioisosteric replacement of a carboxamide group by a sulfonamide moiety on the N-glycosidic torsions as well as on molecular assembly, several glycosyl methanesulfonamides and glycosyl chloromethanesulfonamides were synthesized as analogues of the N-glycoprotein linkage region, and crystal structures of seven of these compounds have been solved. A comparative analysis of this series of crystal structures as well as with those of the corresponding alkanamido derivatives revealed that N-glycosidic torsion, φN, does not alter significantly. Methanesulfonamido and chloromethanesulfonamido derivatives of GlcNAc display a different aglycon conformation compared to other sulfonamido analogues. This may be due to the cumulative effect of the direct hydrogen bonding between N1 and O1′ and C-H×××O interactions of the aglycon chain, revealing the uniqueness of the GlcNAc as the linkage sugar. Unique molecular assembly motif of GlcNAc: The different aglycon conformations of methanesulfonamido and chloromethanesulfonamido derivatives of GlcNAc as compared to other sulfonamido analogues is a unique feature of their molecular assembly. This could be due to the cumulative effect of the direct hydrogen bonding between N1 and O1′ and C-H×××O interactions of the aglycon chain. Copyright © 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Chemistry - A European Journal

Exploring the effect of bioisosteric replacement of carboxamide by a sulfonamide moiety on N-glycosidic torsions and molecular assembly: Synthesis and x-ray crystallographic investigation of n-(β- D -glycosyl)sulfonamides as n-glycoprotein linkage region analogues

The biological addition of oligosaccharide moieties to asparagine residues of N-glycoproteins influences the properties and bioactivities of these macromolecules. The low-temperature neutron crystal structures of three N-glycoprotein linkage models and analogues provide accurate characterization of the three-dimensional structure of the conserved GlcNAc - Asn linkage. These first crystal structures of N-acetylated carbohydrates obtained by neutron diffraction provide high-resolution geometrical parameters that can be used for force-field parametrization and subsequent molecular dynamics simulation of N-glycoproteins. The correct localization of hydrogen atoms demonstrates the occurrence of trifurcated hydrogen bonds and hydrophobic contacts. © 2011 American Chemical Society.

Journal	Acta Crystallographica Section C: Crystal Structure Communications
Publisher	Blackwell Munksgaard
ISSN	01082701
Open Access	No