title: Vieillardiixanthone B.
abstract: THE TITLE COMPOUND [SYSTEMATIC NAME: 1,5-dihydr-oxy-3,6-dimeth-oxy-4-(2-methyl-but-3-en-2-yl)-9H-xanthen-9-one], C(20)H(20)O(6), is a xanthone, which was isolated from the roots of Cratoxylum formosum ssp. pruniflorum. The three rings in the mol-ecule are approximately coplanar, with an r.m.s. deviation of 0.0372 (2) Å for the plane through the 14 non-H atoms. The O atoms of the two hydr-oxy substituents also lie close to this plane with deviations of 0.0669 (2) and 0.1122 (2) Å, respectively. The 1,1-dimethyl-2-propenyl substituent is in a (-)-anti-clinal conformation. Intra-molecular O-H⋯O hydrogen bonds generate S(5) and S(6) ring motifs. In the crystal, mol-ecules are linked into infinite chains along [010] by O-H⋯O hydrogen bonds and weak C-H⋯O inter-actions. π-π inter-actions with centroid-centroid distances of 3.6172 (10) and 3.6815 (10) Å are also observed.
authors.forename: Nawong
authors.initials: N
authors.lastname: Boonnak
authors.forename: Suchada
authors.initials: S
authors.lastname: Chantrapromma
authors.forename: Hoong-Kun
authors.initials: HK
authors.lastname: Fun
authors.forename: Chatchanok
authors.initials: C
authors.lastname: Karalai