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.

Keywords: crystal structure.

Fig. 1.

ORTEP plot (Johnson, 1965) of the asymmetric unit showing the atomic numbering scheme. The probability ellipsoids are drawn at the 50% probability level. The disordered part is drawn with open bonds for the fragment where the atoms have site occupation factors of 0.443 (4).

Fig. 2.

Stereoscopic ORTEP plot (Johnson, 1965) of molecule 1 showing the atomic numbering scheme. The probability ellipsoids are drawn at the 50% probability level.

Fig. 3.

Stereoscopic ORTEP plot (Johnson, 1965) of molecule 2 showing the atomic numbering scheme. The probability ellipsoids are drawn at the 50% probability level. The disordered part is drawn with open bonds for the fragment where the atoms have site occupation factors of 0.443 (4).