(E)-1-[4-(Methylsulfanyl)phenyl]-2-(2,3,4-trimethoxyphenyl)ethene

In the title compound, C18H20O3S, the rings are almost coplanar [inter-ring dihedral angle = 6.6 (2)°]. In the crystal, weak C—H⋯O hydrogen bonds between the methoxy groups connect adjacent molecules, giving chains which extend along [001].

In the title compound, C 18 H 20 O 3 S, the rings are almost coplanar [inter-ring dihedral angle = 6.6 (2) ]. In the crystal, weak C-HÁ Á ÁO hydrogen bonds between the methoxy groups connect adjacent molecules, giving chains which extend along [001].
This study was supported by the Polish Ministry of Science and Higher Education grant No. N N405 209737.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: ZS2220).
Interest in the concept and practice of chemoprevention as an approach to the control of cancer has increased especially due to the unsatisfactory results of classic chemotherapy. In vitro mechanisms of action of RSV have been extensively discussed in numerous reports and reviews. Several key mechanisms of action include: inhibition of the transcription factor NF-κB, regulation of cytochrome P450 enzymes, activation of nuclear receptors such as estrogen receptors (ERs), inhibition of expression and activity of inflammation-related enzymes such as cyclooxygenases and regulation of sirtuins.
These facts lead to the conclusion that RSV might be the potential lead structure for cancer chemopreventive and chemotherapeutic compounds.
Our previous studies have shown that a series of 4′-methylthio-trans-stilbene derivatives differing in the number and position of additional methoxy groups exhibited high affinity toward active sites of CYP1 enzymes involved in the activation of procarcinogens, in particular CYP1A1, CYP1A2 and CYP1B1. 2,3,4-Trimethoxy-4′-methylthio-transstilbene was found to be the most selective inhibitor of the enzymes CYP1A1 and CYP1B1 (IC 50 values of 0.9 and 1.0 mM respectively, and exerted very low affinity to CYP1A2 (IC 50 value above 50 mM).
Among the three methoxy substituents on the aromatic ring, only that at C14 is approximately coplanar with the benzene ring. The other two, at C15 and C16, are oriented towards opposite sides of the ring (Fig. 1 b)

Experimental
The key synthetic step for the construction of this compound involves the generation of diethyl 4-methylthiobenzyl phosphonate as an intermediate. This was prepared from commercially available 4-methylthiobenzyl alcohol in two steps.
First, 4-methylthiobenzyl alcohol was converted to the chloride using SOCl 2 in toluene at room temperature. Then, through the Michaelis-Arbuzov reaction of the 4-methylthiobenzyl chloride with triethylphosphite at 130 °C the corresponding phosphonate ester was obtained (Ulman et al., 1990). The title compound was prepared by the Wittig-Horner reaction of diethyl 4-methylthiolbenzylphosphonate with the commercially available 2,3,4-trimethoxybenzaldehyde in DMF using sodium hydride as a base (Cushman et al., 1991;Ulman et al., 1990).

Refinement
All hydrogen atoms were found in difference-Fourier maps and were freely refined with isotropic displacement parameters.

Figure 3
The crystal packing viewed down the chain direction [001]. 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 > σ(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.