(2E,4R,5R,6S)-2-(4,5,6-Trihydroxycyclohex-2-en-1-ylidene)acetonitrile

The crystal structure of the title compound, C8H9NO3, is characterized by a complex three-dimensional hydrogen-bond network in which every molecule is connected to six symmetry-related neighbours.

The crystal structure of the title compound, C 8 H 9 NO 3 , is characterized by a complex three-dimensional hydrogen-bond network in which every molecule is connected to six symmetry-related neighbours.

Related literature
For the isolation of this natural product, see: Hua et al. (2004). For previous phytochemical and biological studies of the stem bark of Thecacoris annobonae, see: Kuete et al. (2010).

Ngadjui Comment
Previous phytochemical and biological studies of the stem bark of Thecacoris annobonae (Euphorbiaceae) led to several bioactive secondary metabolites: Kuete et al. (2010). In the continuation of this investigation, the title compound was isolated from the leaves of the same plant using chromatographic methods and characterized by single crystal X-ray diffraction. It should be noted that this natural product was previously obtained from the root of Semiaquilegia adoxoides (Ranunculaceae): Hua et al. (2004).
In the crystal structure of the title compound the six membered ring adopts an envelope conformation in which C(3) is 0.678 (1) Å below the ring plane (Fig. 1). The acrylonitrile group is nearly coplanar to the least square plane of the ring system. The packing is characterized by a complex three-dimensional network formed by hydrogen bonds. Every molecule interacts by hydrogen bonds with six symmetry related molecules. While the hydroxyl groups O7 and O9 are both donor and acceptor of hydrogen bonds, O8 only interacts with N12 via hydrogen bonding ( Fig. 2 and Table 1).

Experimental
Air-dried powder of leaves of Thecacoris annobonae (1.37 kg) was successively macerated with hexane, ethyl acetate and methanol for two days each. Three fractions H (30 g), E (45 g), and M (61 g) were collected. The Methanol fraction M was subjected to a silica gel column chromatography eluted with CH 2 Cl 2 to MeOH gradient yielding 7 mg of this secondary metabolite. It crystallized as needles in three of the fractions eluted with the mixture CH 2 Cl 2 /MeOH in a ratio of 97:3.

Refinement
All hydrogen atoms were located from a difference Fourier map and refined with isotropic displacement parameters. The absolute structure was determined on the basis of 705 Friedel pairs.