Molecular Recognition on Crystallization of Enantiopure and Racemic N-Benzoylalanine Methyl Ester

Abstract

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(2-² H)alanine methyl ester, through molecular recognition on crystallization.