Molecular recognition on crystallization of enantiopure and racemic N-benzoylalanine methyl ester

The melting points of crystals of (S)- and (RS)-N-benzoylalanine methyl ester derived from solutions of ethyl acetate/light petroleum are 56-57.5° and 81.5-82.5°, respectively, reflecting differences in lattice energy that are apparent from the crystal structures. A more extensive mode of association between chains, uniformly stabilized by N-H⋯O=C interactions, is found in the racemate leading to a more efficient packing of molecules. The higher lattice energy of the racemate has been confirmed through the enantiomeric enrichment of an optically active sample and the partial resolution of (RS)-N-benzoyl(2-²H)alanine methyl ester, through molecular recognition on crystallization.