5,7-Dihydroxy-2-(3-hydroxy-4,5-dimethoxyphenyl)-6-methoxy-4H-chromen-4-one

The title compound, C18H16O8, was isolated from the plant Artemisia baldshuanica Krasch et Zarp. The molecule is approximately planar, with the exception of the terminal methyl groups, the C atoms of which devitate from their attached ring planes by 1.243 (5) and 1.168 (5) Å. The dihedral angle between the substituted benzopyran and benzene rings is 5.8 (1)°; this near planarity could be due to conjugation or a packing effect. Intramolecular O—H⋯O and C—H⋯O hydrogen bonds occur. In the crystal, molecules are connected by O—H⋯O hydrogen bonds involving the hydroxy and carbonyl groups, forming hydrogen-bonded chains along [001] and [1-10]. The chains are linked by C—H⋯O interactions.

The title compound, C 18 H 16 O 8 , was isolated from the plant Artemisia baldshuanica Krasch et Zarp. The molecule is approximately planar, with the exception of the terminal methyl groups, the C atoms of which devitate from their attached ring planes by 1.243 (5) and 1.168 (5) Å . The dihedral angle between the substituted benzopyran and benzene rings is 5.8 (1) ; this near planarity could be due to conjugation or a packing effect. Intramolecular O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds occur. In the crystal, molecules are connected by O-HÁ Á ÁO hydrogen bonds involving the hydroxy and carbonyl groups, forming hydrogen-bonded chains along [001] and [110]. The chains are linked by C-HÁ Á ÁO interactions.
The molecule is nearly planar with exception of H 3 C11-and H 3 C12-terminal methyl groups. Substituted benzopyran and phenyl rings are planar with r.m.s. deviations of 0.020 Å and 0.026 Å, respectivily. The angle between ring planes equals to 5.8 (1)° thanks to conjugation of π-electronic systems of cycles. Terminal methyl group carbon atoms (C11 and C12) are deviated from their ring planes to 1.243 (5) Å and 1.168 (5) Å, respectively.

Experimental
Air dry powdered aerial part of Artemisia baldshuanica, collected prebudding period four time extracted with ethanol.
The combined extracts were concentrated under vacuum on a rotary evaporator. Concentrated extract was fractionated with benzene, chloroform, ethylacetate and ethanol. Chloroformic fraction was chromatographed on a silica gel column.
Eluting the column with chloroform-ethanol (50:1) was isolated dark-yellow crystals with m.p 244-245 ° C. Crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution of the compound in ethanol.

Figure 1
Molecular structure of the title compound, displacement ellipsoids are drawn at the 50% probability level.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.16 e Å −3 Δρ min = −0.19 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.008 (2) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.