title: Redetermination and absolute configuration of (+)-7-epiclusianone.
abstract: The absolute configuration of 3-benzoyl-4-hy-droxy-6,6-dimethyl-1,5,7-tris-(3-methyl-but-2-en-yl)bicyclo-[3.3.1]non-3-ene-2,9-dione, C(33)H(42)O(4), isolated from Hypericum hypericoides, has been determined. The previous study [Xiao et al. (2007 ▶). J. Nat. Prod.70, 1779-1782] gave only the established relative configuration. The three stereogenic centers are now established as 1R, 5R and 7S on the basis of the refinement of the Flack absolute structure parameter against Cu Kα data and correspond to a specific rotation of [α](D) (20) = +66°. The enol-hy-droxy group forms an intra-molecular O-H⋯O hydrogen bond to close an S(6) ring.
authors.affiliation: Department of Chemistry, McNeese State University, Lake Charles, LA 70609,  USA.
authors.forename: Omar E
authors.initials: OE
authors.lastname: Christian
authors.forename: Frank R
authors.initials: FR
authors.lastname: Fronczek
authors.forename: Khoa
authors.initials: K
authors.lastname: Ky
authors.forename: Shreedu
authors.initials: S
authors.lastname: Pradhan
authors.forename: Anjela
authors.initials: A
authors.lastname: Manandhar
authors.forename: Cecilia
authors.initials: C
authors.lastname: Richmond