title: Synthesis and X-ray crystallographic investigation of N-(β-D-glycosyl)butanamides derived from GlcNAc and chitobiose as analogs of the conserved chitobiosylasparagine linkage of N-glycoproteins.
abstract: The linkage region, GlcNAcβAsn, is conserved in all eukaryotic N-glycoproteins. As a logical extension of a research endeavor aimed at understanding the structural significance of GlcNAc and Asn as the linkage region constituents, the newer analogs GlcNAcβNHBu and (GlcNAcβ(1-4)GlcNAc)alkanamides have been synthesized to assess the influence of aglycon as well as additional GlcNAc on the linkage region. X-ray crystallographic analysis of the GlcNAcβNHBu and (GlcNAcβ(1-4)GlcNAc)βNHBu is described. Comparative analysis of these structures with those of reported models and analogs shows that the deviation in N-glycosidic torsion, ϕN among the GlcNAc alkanamides is negligible (<2°) whereas (GlcNAcβ(1-4)GlcNAc)βNHBu deviates by ∼15° as compared to GlcNAcβNHBu. Under the influence of the molecular packing, the conformation around the C1'-C2' bond deviates from anti to gauche in (GlcNAcβ(1-4)GlcNAcβNHBu. Interestingly, C2-acetamido group in (GlcNAcβ(1-4)GlcNAc)NHBu orients differently as compared to GlcNAc alkanamides and this orientation was found to be almost similar to β-N,N'-diacetylchitobiose trihydrate. The bifurcated anti-parallel pattern involving N-H⋯O and C-H⋯O hydrogen bonds, a hallmark feature of the N-glycoprotein models, GlcNAcβNHAc and GlcNAcβAsn, is absent in both the title alkanamides. This is the first report on the crystal structure analysis of chitobiosyl alkanamide as analog of the N-glycoprotein linkage region, (GlcNAcβ(1-4)GlcNAc)βAsn.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India. Electronic address: mathi24@gmail.com.
authors.forename: Manoharan
authors.initials: M
authors.lastname: Mathiselvam
authors.forename: Amrita
authors.initials: A
authors.lastname: Srivastava
authors.forename: Babu
authors.initials: B
authors.lastname: Varghese
authors.forename: Serge
authors.initials: S
authors.lastname: Pérez
authors.forename: Duraikkannu
authors.initials: D
authors.lastname: Loganathan
mesh_terms: D000117:Acetylglucosamine / Q000737:chemistry*; D000577:Amides / Q000138:chemical synthesis* / Q000737:chemistry*; D001216:Asparagine / Q000737:chemistry*; D002236:Carbohydrate Conformation; D060326:Chemistry Techniques, Synthetic; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D004187:Disaccharides / Q000737:chemistry*; D006023:Glycoproteins / Q000737:chemistry*; D006031:Glycosylation; D008968:Molecular Conformation
chemical_list: D000577:Amides; D004187:Disaccharides; D006023:Glycoproteins; C032438:chitobiose; D001216:Asparagine; D000117:Acetylglucosamine
keywords: Analogs; Linkage region; N-Glycoprotein; X-ray and molecular assembly