The title compound [systematic name: 7α,12-dihydroxy-8,12-abietadiene,11,14-dione or (4bS,8aS,10R)-3,10-dihydroxy-2-isopropyl-4b,8,8-trimethyl-1,4,4b,5,6,7,8,8a,9,10-decahydrophenanthrene-1,4-dione], C20H28O4, is an abietane diterpenoid, which was isolated from the roots of Premna obtusifolia (Verbenaceae). Its crystal structure has been reported previously [Chen et al. (2000 ▶). Jiegou Huaxue, 19, 122–125], but the absolute configuration could not be determined using data collected with Mo radiation. This redetermination using Cu radiation shows the the absolute configurations of the stereogenic centres at positions 4b, 8a and 10 to be S, S and R, respectively. Two intramolecular O—H⋯O hydrogen bonds [one generating an S(5) ring and one generating an S(6) ring] and a number of short C—H⋯O contacts occur. In the crystal, molecules are linked into infinite chains propagating in [100] by O—H⋯O hydrogen bonds and weak C—H⋯O interactions.
The title compound {systematic name: 5,6,10-trihydroxy-7-isopropyl-1,1,4a-trimethyl-2,3,4,4a-tetrahydrophenanthren-9(1H)-one}, C20H26O4, is a diterpenoid which was isolated from the roots of Premna obtusifolia. The molecule has three fused six-membered rings; the cyclohexane ring is in a twisted-boat conformation and the cyclohexene ring adopts a sofa form. Intramolecular O—H⋯O hydrogen bonds generate two S(5) ring motifs. In the crystal, molecules are linked into infinite one-dimensional chains along the [001] direction by O—H⋯O hydrogen bonds and weak C—H⋯O interactions.
The structure of the title diterpenoid, C20H28O3, {systematic name: (4bS,8aS)-3-hydroxy-2-isopropyl-4b,8,8-trimethyl-4b,5,6,7,8,8a,9,10-octahydrophenanthrene-1,4-dione} is confirmed [Eugster et al. (1993 ▶). Private communication (refcode HACGUN). CCDC, Union Road, Cambridge] and its packing is now described. Its absolute structure was established by refinement against data collected with Cu radiation: the two stereogenic centres both have S configurations. One cyclohexane ring adopts a chair conformation whereas the other cyclohexane ring is in a half-chair conformation and the benzoquinone ring is slightly twisted. An intramolecular O—H⋯O hydrogen bond generates an S(5) ring motif. In the crystal, molecules are linked into chains along [010] by O—H⋯O hydrogen bonds and weak C—H⋯O interactions. The packing also features C⋯O [3.131 (3) Å] short contacts.
In the title compound, C20H28O4, a diterpenoid isolated from the roots of Premna obtusifolia (Verbenaceae), the five-membered ring is in a half-chair conformation. One six-membered ring exists in a twisted-boat conformation while the other is in half-boat conformation. The crystal packing is stabilized by intermolecular O—H⋯O and weak C—H⋯O interactions, generating (001) sheets.
The title compound [systematic name: 14,15-dihydroxy-7,7-dimethyl-13-(propan-2-yl)tricyclo[9.4.0.03,8]pentadeca-1(11),3(8),9,12,14-pentaen-4-one], C20H24O3, is a new icetexane diterpenoid which was isolated from the roots of Premna obtusifolia (Verbenaceae). The molecule has three fused rings: a cyclohexenone, a central cycloheptene and a benzene ring. The cyclohexenone ring is in an envelope conformation, whereas the cycloheptene ring is in a twisted boat conformation. Intramolecular O—H⋯O hydrogen bonds generate S(5) and S(8) ring motifs. In the crystal, molecules are linked into dimers through O—H⋯O hydrogen bonds. These dimers are arranged in to sheets parallel to the ac plane. C—H⋯O and weak C—H⋯π interactions are also present.
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