title: (±)-(4bS,8aR,10aS)-10a-Ethynyl-4b,8,8-trimethyl-3,7-dioxo-3,4b,7,8,8a,9,10,10a-octa-hydro-phenanthrene-2,6-dicarbonitrile.
abstract: The anti-inflammatory and cytoprotective tricyclic title compound, C(21)H(18)N(2)O(2), also known as TBE-31, crystallizes with two nearly superimposable mol-ecules in the asymmetric unit. In both mol-ecules, the three ring systems conform to an envelope-chair-planar arrangement. The central ring, in a cyclohexane chair conformation, contains an axial ethynyl group that bends slightly off from a nearby axial methyl group because of the 1,3-diaxial repulsion between the two groups. In the crystal, weak C-H⋯N and C-H⋯O inter-actions form chains along [001].
authors.affiliation: Institute of Chemical Biology and Drug Discovery, Stony Brook University, Stony Brook, NY 11794,  USA.
authors.forename: Suqing
authors.initials: S
authors.lastname: Zheng
authors.forename: Daniel
authors.initials: D
authors.lastname: Resch
authors.forename: Tadashi
authors.initials: T
authors.lastname: Honda
authors.forename: Jerry P
authors.initials: JP
authors.lastname: Jasinski