A Chirality Chain in Phenylglycine, Phenylpropionic Acid, and Ibuprofen

Abstract

Our strategy to analyze the structures of natural amino acids with respect to the interaction of three different elements of chirality within the molecules was applied to the non-natural amino acid (S)-α-phenylglycine, its analogue (S)-α-phenylpropionic acid, and the drug (S)-ibuprofen. The three chirality elements are the configuration at Cα, the conformation at the Cα-C’ bond, and the distortion of the planar carboxylic group to a flat asymmetric tetrahedron. In all three compounds, a given (S) configuration at Cα predominantly induces (M) conformation at the Cα-C’ bond, which in turn preferentially distorts the carboxylic group to a tetrahedron with (R) configuration. Both steps of this chirality chain display high selectivities. Due to varying co-crystallization partners, in all the structures the molecules are in different environments with respect to packing and hydrogen bonding. Nevertheless, the structural pattern and the diaselectivities of the chirality chain persist. For phenylglycine, DFT (Density Functional Theory) calculations confirm the structural results.

Keywords

• amino acids
• α-phenylpropionic acid
• ibuprofen
• chirality
• diastereoselectivity
• analysis of CSD structures