5-(Hydroxymethyl)furan-2-carboxylic acid

In the title compound, C6H6O4, the furan ring is nearly coplanar with the carboxyl group, the maximum atomic deviation being 0.0248 (9) Å. The crystal packing is stabilized by classical O—H⋯O and weak C—H⋯O hydrogen bonding.

In the title compound, C 6 H 6 O 4 , the furan ring is nearly coplanar with the carboxyl group, the maximum atomic deviation being 0.0248 (9) Å . The crystal packing is stabilized by classical O-HÁ Á ÁO and weak C-HÁ Á ÁO hydrogen bonding.

Comment
In the molecular structure of the compound, all the carbon atoms locate in the same plane. The crystal packing is stabilized by O-H···O and weak C-H···O hydrogen bonding (Table 1).

Experimental
The title compound was obtained from the fermentation of Aspergillus sp. by column chromatography. The strain was isolated from a soil sample collected from Jinjiang salt-field, Fujian, China. The strain was cultured using half sea-water Potato Dextrose Agar medium at 28 degrees celsius for 14 days. The fermentation (40 liters) was extracted with ethyl acetate (EtOAc). The EtOAc extract (18.0 g) eluted with methanol-water (30%, 50%, 70%, 100%; V/V) to yield 12 fractions by column chromatography RP-18. Fraction 1 was further puried by Sephadex LH-20 (140 g) chromatography with methanol.
Then 1-4 eluted with acetone by Sephadex LH-20 (80 g) chromatography, then the main components further puried by silica-gel column chromatography to afford the title compound (8.0 mg).

Refinement
The carboxyl and hydroxy H atoms were located in a difference Fourier map and refined isotropically. Other H atoms were positioned geometrically and were treated as riding on their parent atoms, with C-H distances of 0.93-0.97 Å, and U iso (H) = 1.2U eq (C). Fig. 1. The molecular structure of the title compound with 50% probability ellipsoids.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.