N-Methyl-N-styrylcinnamamide (lansamide) from Clausena lansium in Vietnam

The title compound, C18H17NO, was isolated from the seeds of Clausena lansium (wampee) (Rutaceae). The X-ray crystal structure analysis confirmed its chemical identity and revealed that it is solvent-free, in contrast to the previously reported monohydrate [Huang, Ou & Tang (2006 ▶). Acta Cryst. E62, o1987–o1988]. The molecular structures are practically identical but the molecules pack differently. In contrast to the monohydrate in which the water molecule generates two hydrogen bonds, no such intermolecular contacts are present in the title compound. The dihedral angle between the cinnamamide and the styryl group is 53.1 (1)°.

The title compound, C 18 H 17 NO, was isolated from the seeds of Clausena lansium (wampee) (Rutaceae). The X-ray crystal structure analysis confirmed its chemical identity and revealed that it is solvent-free, in contrast to the previously reported monohydrate [Huang, Ou & Tang (2006). Acta Cryst. E62, o1987-o1988]. The molecular structures are practically identical but the molecules pack differently. In contrast to the monohydrate in which the water molecule generates two hydrogen bonds, no such intermolecular contacts are present in the title compound. The dihedral angle between the cinnamamide and the styryl group is 53.1 (1) .

Related literature
For the structure of the monohydrate, see: Huang et al. (2006). For medicinal applications, see: Loi (2001 gastro-intestinal diseases such as acute and chronic gastrointestinal, ulcers, etc. (Loi, 2001).
The X-ray structure of the monohydrate of (I) was reported recently (Huang et al., 2006) wherein it was reported that "the corresponding anhydrous compound is a pale-yellow liquid at room temperature". Surprisingly, we could grow pale-yellow crystals of the water-free form from n-hexane and its X-ray structure, which is subject of this study, was carried out to confirm its chemical identity.
The molecular structure of (I) is shown in Fig. 1 and its superposition with the molecule found in the monohydrate structure is shown in Fig. 2. Both structures are practically identical with a small difference of 10° in the rotation of the styryl phenyl ring along the bond C11-C12: torsion angle C10-C11-C12-C13= 148.7 (1)° for (I) and 139.0 (3)° for the monohydrate. Bond lengths and angles, which are all in the expected ranges, have an average difference of 0.007 Å and 0.4° between (I) and the monohydrate.
The triclinic lattice of (I) is illustrated in Fig. 3. In contrast to the monohydrate where the water molecule generates two hydrogen bonds in a body centered tetragonal lattice, no such intermolecular contacts are present in (I). Nevertheless, the packing in the triclinic lattice shows some characteristic features. The molecule consists of two planar fragments, the cinnamamide and the styryl group, forming an interplanar angle of 53.1 (1)°. In molecular pairs related by the inversion centre at (1/2, 1/2, 1), the cinnamamide fragments are aligned in parallel planes with a shortest contact distance of C atoms of adjacent planes being C1···C8 = 3.664 (3) Å. Such an arrangement of cinnamamide groups was also observed in the monohydrate structure. The styryl groups also form co-planar planes for molecules related by the inversion centre at (1/2, 1/2, 1/2), the shortest distance between C atoms of adjacent planes is C11···C17 = 3.730 (3) Å (see dashed lines in Fig. 3).
This arrangement of styryl groups was not observed in the monohydrate structure.

Experimental
The dried seeds of C. lansium (3,0 kg) were powdered and extracted with MeOH at room temperature, and the combined extracts were concentrated under reduced pressure to give a deep-brown syrup (160 g). This was partitioned between H 2 O and n-hexane. The n-hexane-soluble residue (85 g) was chromatographed over a silica gel column, which developed by gradient elution with n-hexane and increasing concentrations of Me 2 CO to afford forty fractions. Fractions were combined on their TLC. After standing for several day, fractions 9-11 recrystallized from n-hexane to afford pale-yellow lansamide (2554 mg).
supplementary materials sup-2 Refinement Carbon-bound H-atoms were placed in calculated positions (C-H 0.93 to 0.96 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2 to 1.5U(C). Fig. 1. Molecular structure of (I) with atom numbering scheme, displacement ellipsoids are shown at the 50% probability level.