(–)-(S)-N,N′-Bis[1-(1-naphth­yl)eth­yl]­oxalamide

The title mol­ecule, C(26)H(24)N(2)O(2), displays C (2) symmetry, with the mol­ecule located on a twofold axis perpendicular to the plane of the oxalamide unit –NH—CO—CO—NH–. The oxalamide core deviates from planarity, as reflected by the O=C—C=O and N—C—C—N torsion angles of 164.3 (5) and 163.2 (5)°, respectively. The naphthyl groups are oriented toward the same face of the oxalamide mean plane and make a dihedral angle of 43.76 (8)°. This conformation is suitable for the formation of inter­molecular N—H⋯O hydrogen bonds, giving noncentrosymmetric dimers incorporating R (2) (2)(10) ring motifs. These nonbonding inter­actions propagate along the 6(1) screw axis normal to the mol­ecular twofold axis, resulting in a single-stranded right-handed helix parallel to [001]. In the crystal, Δ helices are arranged side-by-side and inter­act through π–π contacts between naphthyl groups. The shortest centroid–centroid separation between inter­acting benzene rings is 3.623 (4) Å.