Crystal structure of 7β-hydroxyroyleanone isolated from Taxodium ascendens (B.)

The title compound, C20H28O4 [systematic name: (4bS,8aS,10S)-3,10-dihydroxy-2-isopropyl-4b,8,8-trimethyl-4b,5,6,7,8,8a,9,10-octahydrophenanthrene-1,4-dione], is an abietane-type diterpene, which was isolated from Taxodium ascendens (B.). The compound crystallizes in the chiral space group P21, but it was not possible to determine the absolute structure of the molecule in the crystal by resonant scattering. The molecular structure is stabilized by two intramolecular O—H...O hydrogen bonds, enclosing S(5) and S(6) ring motifs. In the crystal, molecules are linked by O—H...O and C—H...O hydrogen bonds, forming chains along the [010] direction. The crystal structure of the 10R stereoisomer of the title compound, isolated from the roots of Premna obtusifolia (Verbenaceae), has been reported. It crystallized in the chiral space group P212121, and the absolute structure was determined as (4bS,8aS,10R), by resonant scattering using Cu Kα radiation [Razak et al. (2010). Acta Cryst. E66, o1566–o1567].