title: Simple Resolution of Enantiomeric NMR Signals of α-Amino Acids by Using Samarium(III) Nitrate With L-Tartarate.
abstract: Readily available L-tartaric acid, which is a bidentate ligand with two chiral centers forming a seven-membered chelate ring, was applied to the chiral ligand for the chiral nuclear magnetic resonance (NMR) shift reagent of samarium(III) formed in situ. This simple method does not cause serious signal broadening in the high magnetic field. Enantiomeric (13)C and (1)H NMR signals and enantiotopic (1)H NMR signals of α-amino acids were successfully resolved at pH 8.0 and the 1:3 molar ratio of Sm(NO3)3:L-tartaric acid. It is elucidated that the enantiomeric signal resolution is attributed to the anisotropic magnetic environment for the enantiomers induced by the chiral L-tartarato samarium(III) complex rather than differences in stability of the diastereomeric substrate adducts. The present (13)C NMR signal resolution was also effective for the practical simultaneous analysis of plural kinds of DL-amino acids.
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
authors.forename: Sen-Ichi
authors.initials: S
authors.lastname: Aizawa
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kidani
authors.forename: Sayuri
authors.initials: S
authors.lastname: Takada
authors.forename: Yumika
authors.initials: Y
authors.lastname: Ofusa
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009566:Nitrates / Q000737:chemistry*; D012493:Samarium / Q000737:chemistry*; D013237:Stereoisomerism; D013644:Tartrates / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D009566:Nitrates; D013644:Tartrates; D012493:Samarium; C029768:tartaric acid
keywords: 13C and 1H NMR; L-tartaric acid; chiral shift reagent; samarium(III) complex; simultaneous analysis