8-Hydroxy-6-methoxy-7-(3-methylbut-2-enyloxy)coumarin (capensine)

The title coumarin derivative was isolated from the plants of Sophora japonica. In the crystal, molecules are linked by O—H⋯O and C—H⋯O hydrogen bonds into chains along the [101] direction.


data reports
isolated from the roots of Sophora japonica. Slow evaporation from a solution in methanol yielded monoclinic crystals with space group P2 1 /n with one crystallographically independent molecule. The molecular structure of the title compound is presented in Fig. 1. The benzopyran ring system is practically planar, the r.m.s. deviation from planarity being 0.0356 Å . The methoxy substituent at atom C8 lies almost within the plane of the benzopyran oxa-heterocycle. The torsion angle C7-C6-O3-C10 is 178.18 (3). The 3-methylbut-2-enyloxy substituent at atom C7 is disordered over two sets of sites by a rotation around the C11-C12 bond. The two orientations are not equivalent -the site occupation factors are 0.920 (3) and 0.080 (3).

Synthesis and crystallization
The title compound was isolated from the roots of Sophora japonica. The roots (2.5 kg) of S. japonica were extracted with ethanol at room temperature, which afforded a light-yellow residue (228.1 g) after solvent evaporation under reduced pressure. The residue was diluted with water (1:1), washed with non-polar solvents (hexane, petroleum ether, gasoline) to remove lipophilic substances, and then subjected to sequential liquid-liquid extraction with chloroform, ethyl acetate, and n-butanol. The obtained chloroform fraction (30.4 g) was subjected to column chromatography on silica gel in gradient solvent systems; coumarins were isolated from the eluates obtained by repeated chromatography on a polyamide sorbent, preparative TLC on Silufol UV-254 in the following system: chloroform-petroleum ether-ethanol (8:2:2), R f = 0.74 and fractional crystallization from chloroform. The yield of capensine was 55 mg (0.0022%), m.p. 139-141 C. Suitable crystals for X-ray structural analysis were obtained by slow evaporation from a solution in methanol at room temperature.

Figure 2
Crystal structure of the title compound in a projection on the (101) plane. Intermolecular hydrogen bonds are shown as dashed lines. The figure shows only the major occupancy component of the disordered 3methylbut-2-enyloxy substituent at atom C7.

Figure 1
The molecular structure of the title compound with atom labelling. 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 = 0.24 e Å −3 Δρ min = −0.25 e Å −3 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.

data-2
IUCrData (2021). 6, x210451 Refinement. All hydrogen atoms were placed in idealized positions and refined as riding. Methyl and hydroxyl H atoms were allowed to rotate but not to tip to best fit the experimental electron density. U iso (H) values were set to a multiple of U eq (C) with 1.5 for CH 3 and OH, and 1.2 for C-H and CH 2 units, respectively.