Crystal structure of diacetate of demethylsalvicanol, C24H34O5
Zeitschrift für Kristallographie - New Crystal Structures
Source of material: The title compound was extracted from the roots of Salvia aspera and crystallized from a mixture hexane/ethyl acetate by slowly evaporation. Refinement of absolute configuration by Flack's method was not conclusive, so the atom coordinates and the figure show the stereochemistry relative to CIO(R) as found in salvicanol 11-p-bromobenzoate. The H-atom attached to OlO was located on an electron difference map and its coordinates refined. A fixed isotropic thermal parameter и =
... ermal parameter и = 0.06 Â^ was used for all the hydrogen atoms. The title compound is the diacetyl derivative of demethylsalvicanol, an icetexane-type diterpenoid previously isolated from Salvia mellifera, whose structure was established by comparison with salvicanol. The A/B junction in salvicanol was firmly established to be trans, by X-ray analysis (see ref. 1). Based on possible biogenetic correlations with salvicanol, the demethylsalvicanol was proposed as A/B trans fused, however, spectroscopic data were not conclusive. The six and seven-membered trans [T4,5,10,i = ^5.0(6)° and T6,5,10,20 = 64.9(5)°] fused rings A and В adopt chair conformations, while the aromatic ring С is essentially planar. The hydroxy and acetoxy substituents are located on the ß-face of the tricyclic skeleton. The acetoxy groups are nearly perpendicular to the aromatic ring, and that attached to С11 makes an intramolecular hydrogen bond [OIO-HIO, 0.82(6) A; H10--021, 2.22(7) Â; 010 -021, 2.993(6) Â; 01(>-Η10···021, 156(6)°]. The orientation of the isopropyl substituent is such that the plane of the aromatic ring bisects the angle CH3-CH-CH3, with methyl groups directed away from the acetoxy attached to С12. No unusual features were observed for bond lenths and angles. Crystal packing is entirely due to van der Waals forces.