9-(2-Hy­droxy-4,4-dimethyl-6-oxocyclo­hex-1-en-1-yl)-3,3-dimethyl-2,3,4,9-tetra­hydro-1H-xanthen-1-one

The cyclo­hexene ring that constitutes a part of the tetra­hydroxanthene fused-ring system of the title compound, C(23)H(26)O(4), adopts a flattened half-chair conformation that approximates an envelope conformation (in which the methyl­ene C atom bearing the two methyl substituents represents the flap) as five of the six atoms lie approximately on a plane (r.m.s. deviation = 0.020 Å). The mean plane of the cyclo­hexene ring with the hy­droxy substituent is approximately perpendicular to the mean plane of the tetra­hydroxanthene system. In the crystal, adjacent mol­ecules are linked by O—H⋯O(carbon­yl) hydrogen bonds into a chain running along the b axis.