Gas‐Phase Conformational Map of the Amino Acid Isovaline

Four conformers of the non‐proteinogenic α‐amino acid isovaline, vaporized by laser ablation, are characterized by Fourier‐transform microwave techniques in a supersonic expansion. The comparison between the experimental rotational and 14N nuclear quadrupole coupling constants and the ab initio calculated ones provides conclusive evidence for the identification of the conformers. The most stable species is stabilized by an N−H⋅⋅⋅O =C intramolecular hydrogen bond and a cis‐COOH interaction, whereas the higher‐energy conformers exhibit an N⋅⋅⋅H−O intramolecular hydrogen bond and trans‐COOH, as in other aliphatic amino acids. The spectroscopic data herein reported can be used for the astrophysical purpose in a possible detection of isovaline in space. Identifying isomers: Isovaline, a compound found in meteorites and a biological relevant non‐proteinogenic α‐amino acid, has been studied using rotational spectroscopy in the gas phase. Four conformers stabilized by different intermolecular interactions have been detected. The spectroscopic data reported are prerequisite for an astrophysical detection in space.