Crystal structure of β-d,l-psicose

Abstract

The title compound, C6H12O6, a C-3 position epimer of fructose, was crystallized from an aqueous solution of equimolar mixture of d- and l-psicose (1,3,4,5,6-pentahydroxyhexan-2-one, ribo-2-hexulose, allulose), and it was confirmed that d-psicose (or l-psicose) formed β-pyranose with a 2C5 (or 5C2) conformation. In the crystal, an O—H...O hydrogen bond between the hydroxy groups at the C-3 and C-2 positions connects homochiral molecules into a column along the b axis. The columns are linked by other O—H...O hydrogen bonds between d- and l-psicose molecules, forming a three-dimensional network. An intramolecular O—H...O hydrogen bond is also observed. The cell volume of racemic β-d,l-psicose [763.21 (6) Å3] is almost the same as that of chiral β-d-psicose [753.06 Å3].

Keywords

• crystal structure
• hydrogen bonding
• racemic compound
• rare sugar