Methyl 2-acetamido-2-deoxy-β-dglucopyranoside dihydrate and methyl 2-formamido-2-deoxy-β-dglucopyranoside

Abstract

Methyl 2-acetamido-2-deoxy-β-dglucopyranoside (β-GlcNAcOCH 3), (I), crystallizes from water as a dihydrate, C9H 17NO6·H2O, containing two independent molecules [denoted (IA) and (IB)] in the asymmetric unit, whereas the crystal structure of methyl 2-formamido-2-deoxy-β-dglucopyranoside (β-GlcNFmOCH3), (II), C8H15NO6, also obtained from water, is devoid of solvent water molecules. The two molecules of (I) assume distorted 4 C 1 chair conformations. Values of ψ for (IA) and (IB) indicate ring distortions towards B C 2,C5 and C3,O5 B, respectively. By comparison, (II) shows considerably more ring distortion than molecules (IA) and (IB), despite the less bulky N-acyl side chain. Distortion towards B C 2,C5 was observed for (II), similar to the findings for (IA). The amide bond conformation in each of (IA), (IB) and (II) is trans, and the conformation about the C - N bond is anti (C - H is approximately anti to N - H), although the conformation about the latter bond within this group varies by 16°. The conformation of the exocyclic hydroxymethyl group was found to be gt in each of (IA), (IB) and (II). Comparison of the X-ray structures of (I) and (II) with those of other GlcNAc mono- and disaccharides shows that GlcNAc aldohexopyranosyl rings can be distorted over a wide range of geometries in the solid state. © 2011 International Union of Crystallography.