title: Redetermined crystal structure of N-(β-carb-oxy-eth-yl)-α-isoleucine.
abstract: Redetermination of the crystal structure of N-(β-carb-oxy-eth-yl)-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 mol-ecule 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 inter-molecular inter-actions along with a C-H⋯O hydrogen bond. The inter-molecular inter-action pattern is a three-dimensional network. The structure was refined as a two-component perfect inversion twin.
authors.affiliation: Department of Physics, Thiagarajar College, Madurai 625 009, Tamil Nadu, India.
authors.forename: M
authors.initials: M
authors.lastname: Chandrarekha
authors.affiliation: Department of Physics, Thiagarajar College, Madurai 625 009, Tamil Nadu, India.
authors.forename: N
authors.initials: N
authors.lastname: Srinivasan
authors.affiliation: Department of Physics, Thiagarajar College, Madurai 625 009, Tamil Nadu, India.
authors.forename: R V
authors.initials: RV
authors.lastname: Krishnakumar
keywords: amino acids; crystal structure; hydrogen bonding; ionization state; isoleucine