(2E,5E)-2,5-Bis(4-hydroxy-3-methoxybenzylidene)cyclopentanone ethanol monosolvate

In the title structure, C21H20O5·C2H5OH, the curcumine-type molecule has a double E conformation for the two benzylidene double bonds [C=C = 1.342 (4) and 1.349 (4) Å] and is nearly planar with respect to the non-H atoms (r.m.s. deviation from planarity = 0.069 Å). The two phenolic OH groups form bifurcated hydrogen bonds with intramolecular branches to adjacent methoxy O atoms and intermolecular branches to either a neighbouring molecule or an ethanol solvent molecule. The ethanol O atom donates a hydrogen bond to the keto O atom. These hydrogen bonds link the constituents into layers parallel to (101) in the crystal structure.

In the title structure, C 21 H 20 O 5 ÁC 2 H 5 OH, the curcumine-type molecule has a double E conformation for the two benzylidene double bonds [C C = 1.342 (4) and 1.349 (4) Å ] and is nearly planar with respect to the non-H atoms (r.m.s. deviation from planarity = 0.069 Å ). The two phenolic OH groups form bifurcated hydrogen bonds with intramolecular branches to adjacent methoxy O atoms and intermolecular branches to either a neighbouring molecule or an ethanol solvent molecule. The ethanol O atom donates a hydrogen bond to the keto O atom. These hydrogen bonds link the constituents into layers parallel to (101) in the crystal structure.

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Acta Cryst. The title structure contains a curcumin analogue synthesized from vanillin (4-hydroxy-3-methoxybenzaldehyde) and cyclopentanone using acidic catalysis (Sardjiman et al., 1997). This curcumin analogue showed good activities as anticancer agent in T47D cell line tests, and has also antioxidant and anti-inflammatory properties (Ohori et al., 2006;Da'i et al., 2007;Anand et al., 2008). As an extension of the work on this compound (Sardjiman et al., 1997;Da'i et al., 2007) we report here the crystal structure of (I), an ethanol solvate. The curcumin type molecule contains two double bonds between C2 and C6 and C5 and C14 which connect the cyclopentanone fragment to the 4-hydroxy-3-methoxybenzylidene groups in E configuration relative to the carbonyl group. The entire molecule is essentially planar with respect to non-hydrogen atoms. The keto-diene system shows usual bond distances and angles. While the angles C1-C2=C6 = 118.9 (3)° and C1-C5=C14 = 118.7 (3)° are close to the ideal C sp2 bond angle of 120°, the bond angles C2=C6 -C7 = 132.3 (3)° and C5=C14-C15 = 132.5 (3)° are large in response to intramolecular H···H contacts (phenyl H6 and H14 with the C 2 H 4 group of the cyclopentanone ring). A partial conjugation between the C2=C6 and C5=C14 double bonds and the carbonyl group C1=O1 is evident from the bond lengths table. All other bond lengths and angles adopt usual values (Du et al., 2010(Du et al., , 2011. In the crystal structure the curcumin type molecules are oriented approximately parallel to (203) and form together with the ethanol solvent molecules layer-like assemblies parallel to (101) linked via hydrogen bonds (Table 1). The two phenolic OH groups form bifurcated hydrogen bonds with intramolecular branches to adjacent methoxy O atoms (O3-H12···O5, O5-H20···O4) and intermolecular branches to either a neigbour molecule (O3-H12···O5 i ) or an ethanol molecule (O5-H20···O6 ii ). Ethanol donates a hydrogen bond to the keto-oxygen atom.

Experimental
The compound was synthesized according to Sardjiman et al. (1997). It was then dissolved in boiling ethanol and crystallized by slow cooling giving yellowish crystals that were stored in cold ethanol prior to X-ray analysis.

Figure 1
The asymmetric unit of (I), with the atomic numbering scheme. The thermal ellipsoids are scaled to 50% probability level.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.14 e Å −3 Δρ min = −0.21 e Å −3 Special details Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 σ(F 2 ) is used only for calculating R-factor (gt).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq O1 0.8369 (