3-(4-Hydroxy-3-methoxyphenyl)acrylic acid–2,3,5,6-tetramethylpyrazine (2/1)

The asymmetric unit of the title compound, C8H12N2·2C10H10O4, contains a tetramethylpyrazine molecule, situated about an inversion center, and two substituted acrylic acid derivatives. The dihedral angle between the phenyl and pyrazine rings is 69.45 (9)°. In the crystal, intermolecular O—H⋯O, O—H⋯N hydrogen bonds and weak C—H⋯O interactions lead to the formation of a supramolecular network. The acrylic acid side chain is positionally disordered [occupancy ratio 0.852 (7):0.148 (7)].

The asymmetric unit of the title compound, C 8 H 12 N 2 Á-2C 10 H 10 O 4 , contains a tetramethylpyrazine molecule, situated about an inversion center, and two substituted acrylic acid derivatives. The dihedral angle between the phenyl and pyrazine rings is 69.45 (9) . In the crystal, intermolecular O-HÁ Á ÁO, O-HÁ Á ÁN hydrogen bonds and weak C-HÁ Á ÁO interactions lead to the formation of a supramolecular network. The acrylic acid side chain is positionally disordered [occupancy ratio 0.852 (7):0.148 (7)].

Comment
The title compound, tetramethylpyrazine ferulate is a pharmacologically significant compound which we found in some prescriptions of traditional Chinese medicine, and which are used to treat stroke patients. In both the invivo and invitro experiments, tetramethylpyrazine ferulate has a remarkable inhibitory effect on ADP induced platelet aggregation (Tan et al., 2003). In order to study further its pharmacological effects the title compound was synthesized by the reaction of 3-(4-hydroxy-3-methoxyphenyl)-2-acrylicacid with tetrathylpyrazine, and its crystal structure is reported on herein.
X-ray crystallographic analysis confirmed the molecular structure and the atom connectivity for the title compound, as illustrated in Fig. 1. The dihedral angle between the mean planes of the pyrazine ring and phenyl ring (C8-C13) is 69.45 (9)°.
In the crystal intermolecular O-H···N hydrogen bonds and weak C-H···O interactions are observed, leading to the formation of a supra-molecular network (Table 1).

Experimental
The title compound was synthesized according to the published procedure (Tan, 2004). Tetramethylpyrazine (2.8 g) was heated with 3-(4-hydroxy-3-methoxyphenyl)-2-acrylicacid (4.0 g) in acetone (45 ml). After refluxing at 333 K for 1 h, the reaction mixture was left to stand for several days, and yellow crystals were finally isolated.