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

The title compound, alternatively called d-fructose-2-amino­isobutyric acid (FruAib), C(10)H(19)NO(7), (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 (2) C (5) 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.