title: 3β-Hydroxy-28-norolea-12,17-dien-11-one.
abstract: The title compound, C29H44O2, was formed by treatment of 11-oxooleanolic acid under strong alkaline conditions. The absolute structure of the chiral mol-ecules could not be determined reliably from the diffraction data, but is known from other triterpenes. The asymmetric unit consists of two mol-ecules, 1 and 2. In both mol-ecules, rings A and B show chair conformations. The other rings show mixed forms between envelope and half-chair conformations with atoms in positions 8, 15 and 21 forming the flaps in rings C, D and E, respectively. Rings D and E of mol-ecule 2 are disordered over two orientations, with occupancies of 0.557 (4) and 0.443 (4), which differ in the direction of the flap in ring E. In the crystal, mol-ecules 1, as well as the mol-ecules 2, are linked by O-H⋯O hydrogen bonds, forming chains parallel to the b axis.
authors.affiliation: Institute of Pharmaceutical Sciences, Department of Pharmaceutical Chemistry, Karl-Franzens University Graz, Schubertstrasse 1, A-8010 Graz, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Seebacher
authors.affiliation: Institute of Pharmaceutical Sciences, Department of Pharmaceutical Chemistry, Karl-Franzens University Graz, Schubertstrasse 1, A-8010 Graz, Austria.
authors.forename: Robert
authors.initials: R
authors.lastname: Weis
authors.affiliation: Institute of Pharmaceutical Sciences, Department of Pharmaceutical Chemistry, Karl-Franzens University Graz, Schubertstrasse 1, A-8010 Graz, Austria.
authors.forename: Johanna
authors.initials: J
authors.lastname: Faist
authors.affiliation: Institute of Chemical Technology of Organic Materials, Erzherzog-Johann University, Stremayrgasse 26/1, A-8010 Graz, Austria.
authors.forename: Robert
authors.initials: R
authors.lastname: Saf
authors.affiliation: Institute of Chemistry, Karl-Franzens University Graz, Schubertstrasse 1, A-8010 Graz, Austria.
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Belaj
keywords: crystal structure