Redetermined crystal structure of N-(β-carboxyethyl)-α-isoleucine

Abstract

Redetermination of the crystal structure of N-(β-carboxyethyl)-α-isoleucine, C9H18N2O3, reported earlier by Nehls et al. [Acta Cryst. (2013), E69, o172–o173], was undertaken in which the ionization state assigned to the molecule as unionized has been modified as zwitterionic in the present work. Single-crystal X-ray intensity data obtained from freshly grown crystals and freely refining the amino H atoms provide enhanced refinement and structural parameters, particularly the hydrogen-bonding scheme. N—H...O hydrogen bonds dominate the intermolecular interactions along with a C—H...O hydrogen bond. The intermolecular interaction pattern is a three-dimensional network. The structure was refined as a two-component perfect inversion twin.

Keywords

• crystal structure
• amino acids
• ionization state
• hydrogen bonding
• isoleucine