title: Redetermination and absolute configuration of berkeleydione.
abstract: The crystal structure of the title compound, berkeleydione [systematic name; (5aS,7R,9S,11R,11aS)-methyl 9-hy-droxy-1,1,5,7,9,11a-hexa-methyl-14-methyl-idene-3,8,10-trioxo-1,3,4,5a,6,7,8,9,10,11,11a,12-dodeca-hydro-7,11-methano-cycloocta-[4,5]cyclo-hepta-[1,2-c]pyran-11-carboxyl-ate], C26H32O7, has been reported previously [Stierle et al. (2004 ▶). Org. Lett. 6, 1049-1052]. However, the absolute configuration could not be determined from the data collected with Mo Kα radiation and has now been determined by refinement of the Flack parameter with data collected using Cu Kα radiation. It is in agreement with the previous circular dichroism assignment, and the crystal packing is similar to that described previously.
authors.affiliation: Department of Biological and Pharmaceutical Sciences, University of Montana, 32 Campus Dr., Missoula, Montana 59812, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Stierle
authors.affiliation: Department of Biological and Pharmaceutical Sciences, University of Montana, 32 Campus Dr., Missoula, Montana 59812, USA.
authors.forename: Donald
authors.initials: D
authors.lastname: Stierle
authors.affiliation: Department of Biological and Pharmaceutical Sciences, University of Montana, 32 Campus Dr., Missoula, Montana 59812, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Decato
keywords: Berkeley pit; absolute structure; crystal structure; helicity rule; resonant scattering