5,8-Dihy-droxy-2,2-dimethyl-12-(3-methyl-but-2-en-yl)pyrano[3,2-b]xanthen-6-one (brasixanthone B).

The title compound (trivial name brasixanthone B), C23H22O5, 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-methyl-but-2-enyl side chain. The core xanthone moiety is almost planar, with a maximum deviation 0.057 (4) Šfrom the mean plane. In the mol-ecule, an intra-molecular O-H⋯O hydrogen bond forms an S(6) ring motif. The crystal structure features inter-molecular O-H⋯O and C-H⋯O inter-actions.