Semisynthetic roxburghin tetra­methyl ether

Alex Saez; Carmen Ramirez de Arellano; Noureddine El Aouad; Silvia Rodriguez; Felipe Otalvaro; Diego Cortes; Jairo Saez

doi:10.1107/S1600536808018266

. 2008 Jun 19;64(Pt 7):o1305. doi: 10.1107/S1600536808018266

Semisynthetic roxburghin tetramethyl ether

Alex Saez ^a,^b,^*, Carmen Ramirez de Arellano ^c, Noureddine El Aouad ^d, Silvia Rodriguez ^a, Felipe Otalvaro ^a, Diego Cortes ^d, Jairo Saez ^a

PMCID: PMC2961722 PMID: 21202934

Abstract

The title molecule, (E)-2,3′,4,5-tetramethoxystilbene, C₁₈H₂₀O₄, is virtually planar. The angle between the two benzene rings is 4.06 (6)°. The intermolecular interactions present in the structure are weak. There are C—H⋯O hydrogen bonds and C—H⋯π-electron ring interactions. The molecules are ordered into planes that are parallel to ( Inline graphic 01). The distance between adjacent planes is about 3.3 Å and therefore π–π electron interactions between the aromatic planes are also plausible.

Related literature

For the importance and useful applications of stilbenoid compounds, see: Cushman et al. (1991 ▶); Nakamura et al. (2006 ▶). For the precursors of the title compound, see: Krishnamurty & Maheshwari (1988 ▶); Anjaneyulu et al. (1990 ▶); Wang et al. (1988 ▶); Murillo (2001 ▶).

Experimental

Crystal data

C₁₈H₂₀O₄
M _r = 300.34
Triclinic,
a = 7.9633 (4) Å
b = 9.2454 (5) Å
c = 11.6194 (5) Å
α = 73.400 (2)°
β = 75.479 (3)°
γ = 70.335 (2)°
V = 760.59 (7) Å³
Z = 2
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 150 (2) K
0.35 × 0.10 × 0.04 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: none
8260 measured reflections
4391 independent reflections
2785 reflections with I > 2σ(I)
R _int = 0.025

Refinement

R[F ² > 2σ(F ²)] = 0.047
wR(F ²) = 0.136
S = 0.98
4391 reflections
203 parameters
H-atom parameters constrained
Δρ_max = 0.29 e Å⁻³
Δρ_min = −0.23 e Å⁻³

Data collection: COLLECT (Nonius, 1998 ▶); cell refinement: SCALEPACK (Otwinowski & Minor, 1997 ▶); data reduction: SCALEPACK; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL/PC (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808018266/fb2091sup1.cif

e-64-o1305-sup1.cif^{(18.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808018266/fb2091Isup2.hkl

e-64-o1305-Isup2.hkl^{(215.1KB, 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
C7—H7⋯O3	0.95	2.39	2.7504 (14)	102
C17—H17B⋯O3ⁱ	0.98	2.52	3.4046 (16)	150
C18—H18B⋯O4ⁱⁱ	0.98	2.46	3.4342 (15)	172
C19—H19B⋯O1ⁱⁱⁱ	0.98	2.51	3.4082 (15)	152
C17—H17A⋯Cg2^iv	0.98	2.91	3.7863 (15)	149
C18—H18C⋯Cg1^v	0.98	2.67	3.5578 (14)	151

Open in a new tab

Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) . Cg1 is the centroid of the C1–C6 ring and Cg2 is the centroid of the C11–C16 ring.

Acknowledgments

The authors thank Colciencias and Universidad de Antioquia (Programa de Sostenibilidad) for financial support.

supplementary crystallographic information

Comment

Stilbenoid compounds display significant biological activities (Cushman et al., 1991; Nakamura et al., 2006). Resveratrol and its derivatives deserve considerable attention for their physiological properties and their role in defense mechanisms of the higher plants. The Roxburghin tetramethyl ether (E)-2,3',4,5,-tetramethoxystilbene) that is an analogue of resveratrol, has been originally obtained by modifications of roxburghin (Krishnamurty & Maheshwari, 1988). It has been completely synthesized by the Perkins modified reaction (Anjaneyulu et al., 1990). In addition to the crystal structure determination, we report an efficient synthesis of this product by the cross-metathesis of 3-methoxystyrene and 2,4,5-trimethoxystyrene, the latter having been obtained as a natural product from the bark of Duguetia colombiana (Annonaceae) (Wang et al., 1988; Murillo, 2001).

Experimental

The catalyst (Grubbs second generation, 9 mg, 0.01 mmol), 2,4,5-trimethoxystyrene (39 mg, 0.2 mmol) and 2-methoxystyrene (277 mg, 2.0 mmol) were disolved in dry toluene (10 ml). The solution was refluxed under nitrogen for 24 h at 393 K. The compound was purified by a flash column chromatography with silica gel using hexane/ethylacetate 9:1 as an eluent. The title compound (30.0 mg) was obtained as a yellow powder in a yield of 50.0%.

Suitable crystals (pale yellow needles, 0.35 x 0.10 x 0.04 mm average size) were obtained by slow evaporation in a two solvent system (hexane/ethylacetate 1:1). The identity and purity of the obtained compound was confirmed by spectroscopic methods.

(E)-1,2,4-trimethoxy-5-(3-methoxystyryl)benzene(Roxburghin tetramethyl ether): pale yellow needles, ¹H-NMR: (CDCl₃,300.13 MHz, numeration acording to ellipsoid plot) d 7.42 (d, J= 16.4 Hz, H-7), 7.26 (dd, J = 8.3,7.7 Hz, H-15), 7.12 (s, H-6), 7.12 (d, J= 7.7 Hz, H-16), 7.06 (s, H-12), 6.79 (d, J= 8.3 Hz, H-14), 6.54 (s, H-3), 3.92 (s, C-2-OCH3),3.92 (s, C-1-OCH3), 3.87 (s, C-4-OCH3),3.85 (s, C-13-OCH3); ¹³C (CDCl₃, 75.47 MHz) d 160.2 (C-13), 152.2 (C-4), 150.1 (C-2),143.8 (C-1), 140.0 (C-11), 129.9 (C-15), 127.1 (C-8), 123.7 (C-7), 119.5 (C-16),118.6 (C-5), 113.1 (C-12), 111.9 (C-6), 109.8 (C-14), 98.1 (C-3), 57.1 (C-17), 56.9(C-18), 56.5 (C-19), 55.7 (C-20). EIMS m/z300 (100), 257 (8), 195 (12).