Crystal structure of the acyclic form of 1-de-oxy-1-[(4-methoxyphenyl)(methyl)amino]-d-fructose.

The title compound, C14H21NO6, (I), crystallizes exclusively in the acyclic keto form. In solution of (I), the acyclic tautomer represents only 10% of the population in equilibrium, with the other 90% consisting of β-pyran-ose, β-furan-ose, α-pyran-ose, and α-furan-ose cyclic forms. The carbohydrate chain in (I) has a zigzag conformation and the aromatic amine group has a transitional sp2/sp3 geometry. Bond lengths and valence angles in the carbohydrate portion compare well with the average values for related acyclic polyol structures. All of the hydroxyl groups are involved in inter-molecular hydrogen bonding and form a two-dimensional network of infinite chains, which are inter-linked by intra-molecular hydrogen bonds and organized into R88(16) homodromic ring patterns. A comparative Hirshfeld surfaces analysis of (I) and four other 1-amino-1-de-oxy-d-fructose derivatives suggests the balance of hydro-philic/hydro-phobic inter-actions plays a role in the crystal packing, favoring the acyclic isomer.