5,8-Dihy­droxy-2,2-dimethyl-12-(3-methyl­but-2-en­yl)pyrano[3,2-b]xanthen-6-one (brasixanthone B)

The title compound (trivial name brasixanthone B), C(23)H(22)O(5), isolated from Calophyllum gracilentum, is characterized by a xanthone skeleton of three fused six-membered rings plus an additional fused pyrano ring and one 3-methyl­but-2-enyl side chain. The core xanthone moiety is almost planar, with a maximum deviation 0.057 (4) Å from the mean plane. In the mol­ecule, an intra­molecular O—H⋯O hydrogen bond forms an S(6) ring motif. The crystal structure features inter­molecular O—H⋯O and C—H⋯O inter­actions. [Image: see text]