title: Methyl 5,7-dihydr-oxy-2,2,9-trimethyl-6,11-dioxo-6,11-dihydro-2H-anthra[2,3-b]pyran-8-carboxyl-ate.
abstract: The title compound, C(22)H(18)O(7), also known as laurentiquinone B, is a new anthraquinone which was isolated from Vismia laurentii, a Cameroonian medicinal plant. The asymmetric unit contains two independent mol-ecules. Each of them contains four fused rings, three of which are coplanar and typical of anthracene, while the heterocyclic rings adopt envelope conformations. Intra-molecular O-H⋯O hydrogen bonds result in the formation of two planar rings, which are also almost coplanar with the adjacent rings. In the crystal structure, inter-molecular O-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules and a π-π contact is also present [centroid-centroid distance = 3.967 (3) Å].
authors.forename: Diderot
authors.initials: D
authors.lastname: Noungoue Tchamo
authors.forename: Lydia
authors.initials: L
authors.lastname: Brelot
authors.forename: Cyril
authors.initials: C
authors.lastname: Antheaume
authors.forename: Silvère
authors.initials: S
authors.lastname: Ngouela
authors.forename: Annelise
authors.initials: A
authors.lastname: Lobstein