Methyl 2-(3a,8a-dimethyl-4-oxodeca­hydro­azulen-6-yl)acrylate

Mohamed Tebbaa; Ahmed Benharref; Moha Berraho; Jean Claude Daran; Mohamed Akssira; Ahmed Elhakmaoui

doi:10.1107/S1600536811029928

. 2011 Jul 30;67(Pt 8):o2187–o2188. doi: 10.1107/S1600536811029928

Methyl 2-(3a,8a-dimethyl-4-oxodecahydroazulen-6-yl)acrylate

Mohamed Tebbaa ^a,^*, Ahmed Benharref ^a, Moha Berraho ^a, Jean Claude Daran ^b, Mohamed Akssira ^c, Ahmed Elhakmaoui ^c

PMCID: PMC3213619 PMID: 22091196

Abstract

The title compound, C₁₆H₂₄O₃, was synthesized from ilicic acid, which was isolated from the aerial part of Inula viscosa (L) Aiton [or Dittrichia viscosa (L) Greuter]. The asymmetric unit contains two independent molecules, in each of which the seven-membered ring shows a chair conformation, whereas the five-membered ring presents disorder. In the two molecules, three C atoms in the five-membered ring are disordered over two positions with site-occupancy factors of 0.53/0.47 and 0.83/0.17. The dihedral angle between the two rings is different in the two molecules [31.7 (3) and 47.7 (7)°]. The crystal structure is stabilized by weak intermolecular C—H⋯O hydrogen-bond interactions.

Related literature

For background to the medicinal interest in Inula viscosa (L) Aiton [or Dittrichia viscosa (L) Greuter], see: Shtacher & Kasshman (1970 ▶); Chiappini et al. (1982 ▶); Azoulay et al. (1986 ▶); Bohlman et al. (1977 ▶); Ceccherelli et al. (1988 ▶); Geissman & Toribio (1967 ▶). For conformational analysis, see: Cremer & Pople (1975 ▶). For a related synthesis, see: Barrero et al. (2009 ▶).

Experimental

Crystal data

C₁₆H₂₄O₃
M _r = 264.35
Monoclinic,
a = 6.6954 (3) Å
b = 6.9447 (3) Å
c = 31.6168 (18) Å
β = 90.095 (7)°
V = 1470.10 (12) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 180 K
0.33 × 0.23 × 0.15 mm

Data collection

Agilent Xcalibur Eos Gemini ultra diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2010 ▶) T _min = 0.843, T _max = 1.000
9032 measured reflections
5575 independent reflections
4990 reflections with I > 2σ(I)
R _int = 0.020

Refinement

R[F ² > 2σ(F ²)] = 0.042
wR(F ²) = 0.110
S = 1.06
5575 reflections
356 parameters
19 restraints
H-atom parameters constrained
Δρ_max = 0.14 e Å⁻³
Δρ_min = −0.19 e Å⁻³

Data collection: CrysAlis PRO (Agilent, 2010 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEPIII (Burnett & Johnson, 1996 ▶) and ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶ and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811029928/om2451sup1.cif

e-67-o2187-sup1.cif^{(38.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811029928/om2451Isup2.hkl

e-67-o2187-Isup2.hkl^{(267.4KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811029928/om2451Isup3.cml

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
C112—H11B⋯O11ⁱ	0.93	2.42	3.325 (7)	165
C212—H21A⋯O21ⁱ	0.93	2.45	3.348 (6)	162
C26—H26B⋯O23ⁱⁱ	0.97	2.58	3.427 (6)	146

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

Acknowledgments

The authors thank the Unit of Support for Technical and Scientific Research (UATRS and CNRST) for the X-ray measurements.

supplementary crystallographic information

Comment

The Inula Viscosa (L) is widespread in Mediterranean area and extends to the Atlantic cost of Morocco. It is a well known medicinal plant (Shtacher & Kasshman, 1970; Chiappini et al., 1982) and has some pharmacological activities (Azoulay et al., 1986). This plant has been the subject of chemical investigation in terms of isolating sesquiterpene lactones (Bohlman et al., 1977), sesquiterpene acids (Ceccherelli et al., 1988; Geissman & Toribio, 1967). The ilicic acid is one of the main components of the dichloromethane extract of the Inula Viscosa (L) Aiton or Dittrichia Viscosa (L) Greuter]. The literature report one article on the transformation of the ilicic acid (Barrero et al., 2009). In order to prepare products with high added value, that can be used in the pharmacology and cosmetics industry, we have studied the reactivity of this acid. Thus, from the ilicic acid, we have prepared by the method of Barrero et al. (2009), 2-(4a,8-Dimethyl-1, 2,3,4,4 a,5,6,7- octahydro-naphthalene -2-yl)-acrylic acid methyl ester. The epoxidation of the latter by metachloroperbenzoic acid (mCPBA), followed by the opening of the epoxide obtained by Bi(OTf)3 leads to 2- (3a,8a-Dimethyl-4-oxo-decahydro-azulene-6- yl)-acrylic acid methyl ester with a yield of 50% (see figure 3). The structure of this new derivative (I) of ilicic acid was confirmed by its single-crystal X-ray structure. The asymmetric unit contains two crystallographically independent molecules (Fig.1). Each molecule is built up from two fused five and seven-membered rings.The seven membered ring shows a chair conformation as indicated by Cremer & Pople (1975) puckering parameters QT = 0.7918 (48) Å, θ2 = 38.41 (34)°, φ2 = -33.23 (58)° and φ3 = 171.04 (52)° for the ring (C21, C22···C27)and QT = 0.8658 (51) Å, θ2 = 39.31 (31)°, φ2 = -32.67 (53)° and φ3 = 173.97 (45)° for the other ring (C11,C12···C17). In the first molecule (C11 to C151), the dihedral angle between the rings is 31.7 (3)°. The corresponding value in the second molecule (C21 to C251) is 47.7 (7)°. In the crystal structure, the molecules are linked by C—H···O intermolecular hydrogen bonds into a chains along the a axis (Fig.2).

Experimental

To 3 g (12 mmol) of 2-(4a,8-Dimethyl-1,2,3,4,4a,5,6,7-octahydro- naphthalen-2-yl)-acrylic acid methyl ester dissolved in 40 ml of dichloromethane was added one equivalent of m-chloroperbenzoic acid at 70%. The reaction mixture was stirred at room temperature for 3 h, then treated three times with a solution of sodium bisulfite at 10%. The organic layer was then washed with distilled water three times until neutralization, dried over sodium sulfate, filtered and concentrated under reduced pressure. The residue obtained was chromatographed on silica gel eluting with hexane/ ethyl acetate (98/2) to give quantitatively the corresponding epoxide. 2.5 g (9.4 mmol) of this epoxyde is dissolved with 5% Bi(OTf)3 in 20 ml of dichloromethane. The reaction mixture was left stirring for a period of half an hour and then treated with 10 ml of a solution of sodium bicarbonate to 10%. The organic layer was dried filtered and concentrated under reduced pressure. Chromatography on silica gel, eluting with hexane/ethyl acetate (98/2) of the residue obtained, allowed us to obtain 1.24 g (4.71 mmol) of 2-(3a, 8a-dimethyl-4-oxo-azulene-decahydro-6-yl)-acrylic acid methyl ester. The title compound was recrystallized in dichloromethane.