Chiral ligand-exchange resolution of underivatized amino acids on a dynamically modified stationary phase for RP-HPTLC.
The synthesis of Spi(τ-dec), derived from the selective alkylation of L-spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) at the τ-nitrogen of its heteroaromatic ring, with a linear hydrocarbon chain of 10 carbon atoms, is described here for the first time. Spi(τ-dec) was successfully employed in the past to prepare home-made chiral columns for chiral ligand-exchange high-performance liquid chromatography. In the present article a new method is described, using Spi(τ-dec) as a chiral selector in high-performance thin-layer chromatography (HPTLC): commercial hydrophobic plates were first coated with Spi(τ-dec) and then treated with copper sulfate. The performance of this new chiral stationary phase was tested against racemic mixtures of aromatic amino acids, after appropriate optimization of both the conditions of preparation of the plates and the mobile phase composition. The enantioselectivity values obtained for the studied compounds were higher than those reported in the literature for similar systems. The method employed here for the preparation of chiral HPTLC plates proved practical, efficient, and inexpensive.
Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara, Ferrara, Italia.
Maurizio
M
Remelli
Stefania
S
Faccini
Chiara
C
Conato
D024322:Amino Acids, Aromatic / Q000737:chemistry* / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D003300:Copper / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D012997:Solvents; D013237:Stereoisomerism
D024322:Amino Acids, Aromatic; D007202:Indicators and Reagents; D012997:Solvents; D003300:Copper
HPTLC; amino acid enantiomers; chiral coated stationary phase; chiral separation; ligand-exchange chromatography; spinacine