(S)-Methyl 2-{(S)-2-[bis(4-methoxyphenyl)methylideneamino]-3- hydroxypropanamido}-3-methylbutanoate

The title compound, C₂₄H₃₀N₂O₆, a Schiff base, adopts an extended conformation in which the methoxy groups are essentially coplanar with the aromatic ring to which they are bonded (mean planes fitted through the non-H atoms of each methoxyphenyl group have r.m.s. deviations of 0.078 and 0.044 Å) and the angle between mean planes fitted through the aromatic rings is 87.57 (10)°. An intramolecular N - H⋯N hydrogen bond keeps the imine and amide groups essentially coplanar. A mean plane fitted through these groups has an r.m.s. deviation of 0.0545 Å. Additional O - H⋯O hydrogen bonding parallel with the a axis links the molecules into a hydrogen-bonded chain in the crystal. C - H⋯O and C - H⋯π interactions are found within the crystal packing. The compound has been assigned the S,S configuration on the basis of the chemical synthesis, which used pure homotopic lamino acids, and we have no reason to believe that the compound has epimerized.