Experimental

R factor = 0.059; wR factor = 0.062; data-to-parameter ratio = 9.1. The asymmetric unit of the title compound, C23H23N3O2, contains two molecules in both of which, one amide N atom is in a syn position with respect to the pyridine N atom, while the other amide N atom is in an anti position (the syn--anti conformation). There are minor conformational differences between the two molecules, as reflected in the Npyridine—C— C—Namide torsion angles of 44.9 (3) and 136.0 (2) for one molecule and 43.5 (3) and 131.1 (2) for the other molecule. However, the two molecules show significant differences in the orientation of an ethyl group, with corresponding C—C—N— C torsion angles of 86.6 (3) for one molecule and 79.6 (3) for the other molecule. In the crystal, molecules are linked by weak C—H O hydrogen bonds, forming a three-dimen-sional supramolecular network. Related literature For the extractive properties of some pyridine-dicarbox