New synthetic strategies for the preparation of novel chiral stationary phases for high-performance liquid chromatography containing natural pool selectors

Twelve new chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) were generally prepared starting from the macrocyclic glycopeptide antibiotic teicoplanin, according to novel and efficient ‘one-pot’ synthetic strategies. Their chiral recognition abilities were evaluated under polar-organic mode HPLC, towards a variety of biopharmacological interesting racemates, such as b-amino acids and quaternary ammonium salts (e.g. carnitine and its derivatives). All materials were prepared by two different synthetic strategies, both leading to the formation of one or two stable ureidic functions on the CSP structure. The influence of the different spacers and of the silica matrix nature on the chiral performances was investigated. The obtained results suggested that the optimal synthetic strategy was that leading to the formation of two ureidic functions on the CSP structure, spaced-out by a six-carbon atoms aliphatic chain; the best chromatographic results were reached with the use of the spherical LiChrospher silica gel. Enantioselectivity factors (a) particularly high and short-time analyses characterised the analytical procedures; in addition, analytes lacking in chromophore groups were easily detected by evaporative light scattering (ELS) with no need of preliminary derivatization.