title: Redetermined structure, inter-molecular inter-actions and absolute configuration of royleanone.
abstract: The structure of the title diterpenoid, C(20)H(28)O(3), {systematic name: (4bS,8aS)-3-hy-droxy-2-isopropyl-4b,8,8-trimethyl-4b,5,6,7,8,8a,9,10-octa-hydro-phenanthrene-1,4-dione} is confirmed [Eugster et al. (1993 ▶). Private communication (refcode HACGUN). CCDC, Union Road, Cambridge] and its packing is now described. Its absolute structure was established by refinement against data collected with Cu radiation: the two stereogenic centres both have S configurations. One cyclo-hexane ring adopts a chair conformation whereas the other cyclo-hexane ring is in a half-chair conformation and the benzoquinone ring is slightly twisted. An intra-molecular O-H⋯O hydrogen bond generates an S(5) ring motif. In the crystal, mol-ecules are linked into chains along [010] by O-H⋯O hydrogen bonds and weak C-H⋯O inter-actions. The packing also features C⋯O [3.131 (3) Å] short contacts.
authors.forename: Hoong-Kun
authors.initials: HK
authors.lastname: Fun
authors.forename: Suchada
authors.initials: S
authors.lastname: Chantrapromma
authors.forename: Abdul Wahab
authors.initials: AW
authors.lastname: Salae
authors.forename: Ibrahim Abdul
authors.initials: IA
authors.lastname: Razak
authors.forename: Chatchanok
authors.initials: C
authors.lastname: Karalai