(3S,3aS,5aS,7S,8S,10aS,10bR)-7,8-Dihydr­oxy-3-isopropyl-5a,8-dimethyl-2,3,4,5,5a,6,7,8,10a,10b-deca­hydro­cyclo­hepta­[e]indene-3a(1H)-carboxylic acid

Iván Brito; Jorge Bórquez; Luis Alberto Loyola; Alejandro Cárdenas; Matías López-Rodríguez

doi:10.1107/S1600536808018941

. 2008 Jun 28;64(Pt 7):o1348–o1349. doi: 10.1107/S1600536808018941

(3S,3aS,5aS,7S,8S,10aS,10bR)-7,8-Dihydroxy-3-isopropyl-5a,8-dimethyl-2,3,4,5,5a,6,7,8,10a,10b-decahydrocyclohepta[e]indene-3a(1H)-carboxylic acid

Iván Brito ^a,^*, Jorge Bórquez ^a, Luis Alberto Loyola ^a, Alejandro Cárdenas ^b, Matías López-Rodríguez ^c

PMCID: PMC2961850 PMID: 21202969

Abstract

The molecule of the title compound, C₂₀H₃₂O₄, is built up from three fused five-membered, six-membered and seven-membered rings. The five-membered ring has an envelope conformation, whereas the six- and seven-membered rings have chair conformations. The crystal structure is stabilized by strong intermolecular O—H⋯O hydrogen bonds, forming a three-dimensional network. The absolute configuration was assigned on the basis of earlier chemical studies.

Related literature

For related literature, see: Araya et al. (2003 ▶); Cremer & Pople (1975 ▶); Fuentes et al. (2005 ▶); Loyola et al. (1996 ▶, 2004 ▶); Wickens (1995 ▶).

Experimental

Crystal data

C₂₀H₃₂O₄
M _r = 336.46
Orthorhombic,
a = 11.094 (7) Å
b = 12.728 (10) Å
c = 13.8776 (11) Å
V = 1959.6 (19) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 298 (2) K
0.30 × 0.20 × 0.10 mm

Data collection

Nonius KappaCCD area-detector diffractometer
Absorption correction: none
9149 measured reflections
1922 independent reflections
1836 reflections with I > 2σ(I)
R _int = 0.072

Refinement

R[F ² > 2σ(F ²)] = 0.039
wR(F ²) = 0.117
S = 1.13
1922 reflections
226 parameters
H-atom parameters constrained
Δρ_max = 0.21 e Å⁻³
Δρ_min = −0.14 e Å⁻³

Data collection: COLLECT (Nonius, 2000 ▶); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997 ▶); data reduction: DENZO-SMN; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶) and PLATON (Spek, 2003 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808018941/bt2730sup1.cif

e-64-o1348-sup1.cif^{(22.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808018941/bt2730Isup2.hkl

e-64-o1348-Isup2.hkl^{(92.7KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯O4ⁱ	0.82	1.80	2.613 (3)	170
O3—H3⋯O2ⁱⁱ	0.82	2.01	2.825 (3)	173
O4—H4⋯O3ⁱⁱⁱ	0.82	1.94	2.752 (3)	172
C1—H1B⋯O2	0.97	2.44	2.889 (4)	108
C5—H5B⋯O1	0.97	2.51	3.054 (4)	116
C6—H6B⋯O4	0.97	2.52	2.901 (3)	104
C16—H16A⋯O3	0.96	2.46	2.809 (4)	101

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

LAL thanks the Fondo Nacional de Desarrollo Científico y Tecnológico de Chile for grant 1060339. We thank the Spanish Research Council (CSIC) for providing us with a free-of-charge licence for the Cambridge Structural Database.

supplementary crystallographic information

Comment

Azorella compacta is a compact resinous cushion shrub that grows in the Andes of Peru, Bolivia, Argentina and Chile and has been used in folk medicine. The common name llareta is used for several species of the genus Azorella (Wickens, 1995). Mulinane diterpenes exhibits antiplasmodial (Loyola et al., 2004), anti-Tripanosoma cruzi (Araya et al., 2003) and antihyperglycemic (Fuentes et al., 2005) activities.We have undertaken the X-ray crystal-structure determination of the title compound in order to establish its molecular conformation and relative stereochemistry. We are not able to determine the absolute stereochemistry by X-ray methods and the configuration shown here was chosen to be in accord with that reported in previous chemical studies (Loyola et al., 1996). The structure consists of a mulinic acid skeleton and the isopropyl, methyl groups and carboxylic acid at C3, C5a, C8 and C3b are α-oriented respectively, whereas the hydroxyl groups at C8 and C7 are β-oriented. The cyclopentane (A), cyclohexane (B) and cycloheptene (C) rings are in an envelope, chair and chair conformation respectively [Q₂= 0.435 (2) Å, φ₂= 118.7 (3)° for rig A; Q_T= 0.581 (2) Å, θ = 174.4 (2)°, φ=131 (2)° for ring B; Q_T= 0.634 (2) Å, φ₂=78.4 (6)°, for ring C] (Cremer & Pople, 1975). The A and B and B and C rings are trans and cis-fused respectively. The molecular conformation is stabilized by four intramolecular hydrogen bonds and the crystal structure is stabilized by three intermolecular hydrogen bonds (Table 1).

Experimental

Dried and finely powdered whole plant of Azorella compacta (3,0 kg) were extracted with petroleum ether at room temperature. After filtration, the solvent was evaporated in vacuum yielding a gum (220 g). The concentrated petrol ether extract was adsorbed on silica gel (300 g) and slurried onto the top of a column containing silica gel (2.0 kg) in petroleum ether, and eluted with a petroleum ether/ethyl acetate gradient with increasing amounts of ethyl acetate to produce six fractions. Fraction 2 (100 g) eluted with petroleum ether/ethyl acetate(18:2) was further separated and purified by silica gel column chromatography(petroleum ether/ethyl acetate), 19:1) to give 600 mg of the title compound. The structure were elucidated by analysis of their spectroscopic data. Recrystallization from hexane-ethyl acetate (7:3) at room temperature afforded colourless crystals suitable for X-ray diffraction analysis.