1-(2,6-Dihydroxy-4-methoxyphenyl)-3-phenylpropan-1-oneThis paper is dedicated to Her Royal Highness Princess Maha Chakri Sirindhorn of Thailand on the occasion of her 55th Birthday Anniversary which fell on April 2nd, 2010

Crystal Materials Research Unit, Department of Chemistry, Faculty of Science, Prince of Songkla University, Hat-Yai, Songkhla 90112, Thailand, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science and Technology, Suratthani Rajabhat University, Mueang, Surat Thani 84100, Thailand, Natural Products Research Laboratory, School of Science, Mae Fah Luang University, Muang, Chiang Rai 57100, Thailand, and X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia Correspondence e-mail: suchada.c@psu.ac.th

The title compound, C 16 H 16 O 4 , a dihydrochalcone, was isolated from the rhizomes of Etlingera littoralis. The molecule is twisted with a dihedral angle of 71.69 (6) between the two aromatic rings. The propanone unit makes dihedral angles of 4.07 (6) and 73.56 (7) , respectively, with the 2,6-dihydroxy-4methoxyphenyl and phenyl rings. The methoxy group is approximately coplanar with the attached benzene ring with a dihedral angle of 1.74 (10) . An intramolecular O-HÁ Á ÁO hydrogen bond generates an S(6) ring motif. In the crystal, intermolecular O-HÁ Á ÁO hydrogen bonds link the molecules into chains along [201]. Ainteraction with a centroidcentroid distance of 3.5185 (6) Å is also observed.
As part of our study of chemical constituents and bioactive compounds from the rhizomes of Etlingera littoralis which were collected from Surat Thani province in the southern of Thailand, the title dihydrochalcone, (I), was isolated. Herein we report its crystal structure. The title compound was found to possess antibacterial (Nowakowska, 2007) and antiplasmodial activities (Portet et al., 2007).
In the crystal packing (Fig. 2) , O-H···O hydrogen bonds (Table 1) formed between the two hydroxy groups link the molecules into chains along the [201] direction in which the adjacent chains are in anti-parallel manner. A π-π interaction with Cg1···Cg1 distance of 3.5185 (6) Å was observed (symmetry code x, -y, -1/2+z); Cg1 is the centroid of the C1-C6 benzene ring.

Experimental
The fresh rhizomes of E. littoralis (3.89 kg) were chopped and extracted with 50% CH 2 Cl 2 -MeOH, over the period of 3 days at room temperature. The extraction was filtered and evaporated to dryness under reduced pressure to give crude extract which was further partitioned with water and CH 2 Cl 2 to afford the dichloromethane extract (22.88 g). The portion of dichloromethane extract (11.80 g) was subjected to quick column chromatography (QCC) on silica gel eluting with a gradient of EtOAc-hexane to give thirteen fractions. Fraction F8 (322.4 mg) was washed with 20% CH 2 Cl 2 -hexane yielding solid which was further separated by column chromatography on silica gel with 70% CH 2 Cl 2 -hexane to give compound (I) (50.1 mg). Yellow block-shaped single crystals of the compound (I) suitable for X-ray structure determination were obtained from ethyl acetate by slow evaporation at room temperature after a few days, Mp 443 K. The NMR spectral data were consistent with the X-ray structure. atoms. The U iso (H) values were constrained to be 1.5U eq of the carrier atom for hydroxy and methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups. The highest residual electron densitypeak is located at 0.69 Å from C1 and the deepest hole is located at 0.84 Å from C7. A total of 2607 Friedel pairs were merged before final refinement as there is no large anomalous dispersion for the determination of the absolute configuration. Fig. 1. The molecular structure of the title compound, with 50% probability displacement ellipsoids and the atom-numbering scheme.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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 > 2sigma(F 2 ) is used only for calculating R-factors(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.