Supramolecular architectures ofN-acetyl-L-proline monohydrate andN-benzyl-L-proline

Abstract

The title compounds,N-acetyl-L-proline monohydrate, C7H11NO3·H2O, (I), andN-benzyl-L-proline, C12H15NO2, (II), crystallize in the monoclinic space groupP21withZ′ = 1 andZ′ = 2, respectively. The conformation of Cγwith respect to the carboxylic acid group in (I) is Cγ-exoor UP pucker, with the pyrrolidine ring twisted, while in (II), it is Cγ-endoor DOWN, with the pyrrolidine ring assuming an envelope conformation. The crystal packing interactions in (I) are composed of two substructures, one characterized by anR66(24) motif through O—H...O hydrogen bonds and the other by anR44(23) ring through C—H...O interactions. In (II), the crystal packing interactions consist of N—H...O and C—H...O hydrogen bonds. Proline (Pro) exists in its neutral form in (I) and is zwitterionic in (II). This difference in the ionization states of Pro is manifested through the absence of N—H...O and presence of O—H...O interactions in (I), and the presence of N—H...O and absence of O—H...O hydrogen bonds in (II). While C—H...O interactions are present in both (I) and (II), the geometry of the synthons formed by them and their mode of participation in intermolecular interactions is different. Though the title compounds differ significantly in terms of modifications in the Pro skeleton, the differences in their supramolecular structures may also be viewed as a result of the molecular recognition facilitated by the presence of a solvent water molecule in (I) and the zwitterionic state of the amino acid in (II).