Caloxanthone C: a pyran­oxanthone from the stem bark of Calophyllum soulattri

The title compound [systematic name: 5,10-di­hy­droxy-2,2-di­methyl-12-(2-methyl­but-3-en-2-yl)­pyrano[3,2-b]xanthen-6(2H)-one], C(23)H(22)O(5), isolated from the stem bark of Calophyllum soulattri, consists of four six-membered rings and a 2-methyl­but-3-en-2-yl side chain. The tricyclic xanthone ring system is almost planar [maximum deviation = 0.093 (2) Å], whereas the pyran­oid ring is in a distorted boat conformation. The 2-methyl­but-3-en-2-yl side chain is in a synperiplanar conformation. There are two intra­molecular O—H⋯O hydrogen bonds. In the crystal, mol­ecules are linked by C—H⋯O inter­actions, forming a zigzag chain propagating in [010].