(4aS,10aS)-7-Hydroxy-8-isopropyl-1,1,4a-trimethyl-1,2,3,4,4a,9,10,10a-octahydrophenanthrene: a new diterpenoid compound

The new title diterpenoid compound, C20H30O, is a natural product isolated from Tetraclinis articulata wood via chloroform extraction. The asymmetric unit contains four molecules with the same S,S configuration, deduced from the chemical synthesis. Indeed, an overlay analysis, calculated using structure-matching software, shows that the four molecules can be superimposed. The central ring has a half-chair conformation, whereas the saturated ring displays a chair conformation.

The new title diterpenoid compound, C 20 H 30 O, is a natural product isolated from Tetraclinis articulata wood via chloroform extraction. The asymmetric unit contains four molecules with the same S,S configuration, deduced from the chemical synthesis. Indeed, an overlay analysis, calculated using structure-matching software, shows that the four molecules can be superimposed. The central ring has a half-chair conformation, whereas the saturated ring displays a chair conformation.  Table 1 Puckering amplitudes (Cremer & Pople, 1975) for the non-benzenoid rings in the four independent molecules.  Table 2 Structure matching (Å , ) between the four independent molecules.

Related literature
A is the structure match between molecules 1 and 2, B between molecules 1 and 3, C between molecules 1 and 4, D between molecules 2 and 3, E between molecules 2 and 4, and F between molecules 3 and 4. Mazoir, Maya et al. (2007). The title compound (I), was isolated from Tetraclinis articulata wood using extraction with chloroform in a sohxlet apparatus.
The structure of (I) was established by 1 H and 13 C NMR and confirmed by its single-Crystal X-ray structure. The unit cell in space group P1 contains four identical molecules having the same configuration (S,S). Indeed an overlay analyses calculated using the structure matching software (Watkin et al., 2003;Collins et al., 2006) shows that the four molecules could be superimposed (Table 1).
Each of these molecules is built up from three six-membered fused rings, a saturated one and two unsaturated (Fig. 1). The central rings display a half-chair conformation whereas the other unsaturated six-membered ring has a chair conformation (Cremer & Pople, 1975; Table 2).
Experimental 50 g of Tetraclinis articulata wood was extracted with chloroform (300 ml) in a Sohxlet apparatus during 24 h. The CHCl 3 solution was cooled to yield, after solvent removal, one fraction (3.2 g) which was then subjected to silica gel column chromatography using hexane as an eluent afforded compound (I) in 64% yield. Suitable crystals of (I) were obtained by evaporation of a hexane solution at 277 K. m.p. = 373-374 K (hexane); All H atoms attached to C and O atoms were fixed geometrically and treated as riding with C-H = 0.99 Å (methyl), 0.98 Å (methylene), 1.0 Å(methine) or 0.95 Å (aromatic) and O-H = 0.84 Å with U iso (H) = 1.2U eq (C or O) or U iso (H) = 1.5U eq (methyl).

Special details
Geometry. All e.s. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Table 2
Structure matching between the four independent molecules A is the structure match between molecules 1 and 2, B is that between molecules 1 and 3, C is that between molecules 1 and 4, D is that between molecules 2 and 3, E is that between molecules 2 and 4 and F is that between molecules 3 and 4.