Benzyl N-(2-hydroxy-1-{N′-[(1E)-2-hydroxybenzylidene]hydrazinecarbonyl}ethyl)carbamate

The molecule of the title compound, C18H19N3O5, adopts a curved arrangement with the terminal benzene rings lying to the same side. The hydroxylbenzene ring is close to coplanar with the adjacent hydrazine residue [dihedral angle = 11.14 (12)°], an observation which correlates with the presence of an intramolecular O—H⋯N hydrogen bond. The benzyl ring forms a dihedral angle of 50.84 (13)° with the adjacent carbamate group. A twist in the molecule, at the chiral C atom, is reflected in the dihedral angle of 80.21 (12)° formed between the amide residues. In the crystal, two-dimensional arrays in the ac plane are mediated by O—H⋯O and N—H⋯O hydrogen bonds.

The molecule of the title compound, C 18 H 19 N 3 O 5 , adopts a curved arrangement with the terminal benzene rings lying to the same side. The hydroxylbenzene ring is close to coplanar with the adjacent hydrazine residue [dihedral angle = 11.14 (12) ], an observation which correlates with the presence of an intramolecular O-HÁ Á ÁN hydrogen bond. The benzyl ring forms a dihedral angle of 50.84 (13) with the adjacent carbamate group. A twist in the molecule, at the chiral C atom, is reflected in the dihedral angle of 80.21 (12) formed between the amide residues. In the crystal, twodimensional arrays in the ac plane are mediated by O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds.
The use of the EPSRC X-ray crystallographic service at the University of Southampton, England, and the valuable assistance of the staff there is gratefully acknowledged. JLW acknowledges support from CAPES (Brazil).

Comment
The known anti-tumour activity of L-serine derivatives (Jiao et al., 2009;Yakura et al.,2007) motivates the development of N-acylhydrazone derivatives from L-serine for anti-tumour testing Pinheiro et al., 2011a;Pinheiro et al., 2011bHowie et al., 2011), and led to the analysis of (I).
The absolute structure of (I) could not be determined experimentally but, the assignment of the S-configuration at the C9 atom is based on a starting reagent, L-serine. The structure of (I), Fig. 1, adopts a curved conformation with both benzene rings lying to the same side of the molecule. The presence of an intramolecular O-H···N hydrogen bond ensures that the hydroxybenzene group is co-planar with the adjacent hydrazine residue with the dihedral angle between the (O2,N1,N2,C7,C8) and (C1-C6) planes being 11.14 (12) °. By contrast, the benzene ring adjacent to the carbamate residue is twisted as seen in the value of the dihedral angle formed between (O4,O5,N3,C11) and (C13-C18) of 50.84 (13) °. The dihedral angle between the two terminal benzene rings is 75.89 (19) °. The molecule is twisted about the chiral centre with the dihedral angle formed between the two amide residues, i.e. N2,C8,O2 and N3,C11,O4, being 80.21 (12) °.
Hydrogen bonds dominate the crystal packing, Table 1
The O-and N-bound H atoms were located from a difference map and refined with the distance restraints O-H = 0.84 ± 0.01 and N-H = 0.88±0.01 Å, and with U iso (H) = zU eq (carrier atom); z = 1.5 for O and z = 1.2 for N. In the absence of significant anomalous scattering effects, 1896 Friedel pairs were averaged in the final refinement. However, the absolute configuration was assigned on the basis of the chirality of the L-serine starting material. Fig. 1. The molecular structure of (I) showing displacement ellipsoids at the 50% probability level.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes.
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 > 2σ(F 2 ) is used only for calculating Rfactors(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.