Crystal structure and hydrogen bonding in N-(1-deoxy-β-d-fructopyranos-1-yl)-2-aminoisobutyric acid

Abstract

The title compound, alternatively called d-fructose-2-aminoisobutyric acid (FruAib), C10H19NO7, (I), crystallizes exclusively in the β-pyranose form, with two conformationally non-equivalent molecules [(IA) and (IB)] in the asymmetric unit. In solution, FruAib establishes an equilibrium, with 75.6% of the population consisting of β-pyranose, 10.4% β-furanose, 10.1% α-furanose, 3.0% α-pyranose and <0.7% the acyclic forms. The carbohydrate ring in (I) has the normal 2C5 chair conformation and the amino acid portion is in the zwitterion form. Bond lengths and valence angles compare well with the average values from related pyranose structures. All carboxyl, hydroxy and ammonium groups are involved in hydrogen bonding and form a three-dimensional network of infinite chains that are connected through homodromic rings and short chains. Intramolecular hydrogen bonds bridge the amino acid and sugar portions in both molecules. A comparative Hirshfeld surfaces analysis of FruAib and four other sugar–amino acids suggests an increasing role of intramolecular heteroatom interactions in crystal structures with an increasing proportion of C—H bonds.

Keywords

• crystal structure
• fructosamine
• Maillard reaction
• D-fructose-2-aminoisobutyric acid
• hydrogen bonding
• Hirshfeld surface analysis