5,6-Dimethyl-1,2,9,10-tetra­hydro­pyrano[3,2-f]chromene-3,8-dione

The title mol­ecule, C₁₄H₁₄O₄, lies on a twofold rotation axis that bis­ects the central benzene ring, with only one half-mol­ecule in the asymmetric unit. The pyran­one systems adopt distorted twist- boat conformations, with the two methyl­ene C atoms displaced by 0.537 (1) and 0.163 (2) Å from the best-fit plane through the remaining five C and O atoms (r.m.s. deviation = 0.073 Å). In the crystal, bifurcated C—H...(O,O) hydrogen bonds link pairs of adjacent mol­ecules in an obverse fashion, stacking mol­ecules along c. These contacts are further stabilized by very weak π–π inter­actions between adjacent benzene rings with centroid–centroid distances of 4.1951 (4) Å. Additional C—H...O contacts link these stacks, giving a three-dimensional network.

6-Hy­droxy-7,8-dimethyl­chroman-2-one

The title compound, C₁₁H₁₂O₃, is essentially planar, with an r.m.s. deviation of 0.179 Å from the mean plane through the 14 non-H atoms in the mol­ecule. The benzene ring and the pyranone mean plane are inclined at 13.12 (6)° to one another and the pyran­one ring adopts a flattened chair conformation. In the crystal, O—H...O hydrogen bonds and C—H...O contacts form R₁²(6) rings and link mol­ecules into chains along b. Additional C—H...O contacts generate inversion dimers, with R₂²(8) ring motifs, and form sheets parallel to (-102) which are linked by C—H...π interactions.