Crystal structure and absolute configuration of (4S,5R,6S)-4,5,6-trihy-droxy-3-methyl-cyclo-hex-2-enone (gabosine H).

The mol-ecule of the title keto carbasugar, C(7)H(10)O(4), is formed by a cyclo-hexene skeleton with an envelope conformation, substituted by carbonyl, methyl and hydroxyl groups. The crystal structure is controlled mainly by a combination of strong O-H⋯O and weak C-H⋯O hydrogen bonds, forming nearly perpendicular chains running parallel to the [110] and [-110] directions. This perpendicularity is caused by a tetra-gonal pseudosymmetry influenced by the similarity between the a and b axes, the value of 90.9770†(10)° of the β angle and the action of a 2(1) screw axis, which transform each chain into its corresponding nearly orthogonal one.