Mechanistic evaluation of the resolution of α-amino acids on dynamic chiral stationary phases derived from amino alcohols by ligand-exchange chromatography

Dynamic ligand‐exchange chiral stationary phase from S‐benzyl‐(R)‐cysteine

“…4). In this model, which parallels previously reported examples, 15,27 the chiral selector is bound to the octadecyl-silica gel through the hydrophobic interaction of the benzyl group and the sulfur atom intercalated between the RP-18 carbon chains of the original stationary phase. Cu(II) is then coordinated by the bounded chiral selector and the analyte, thus producing a ternary complex that can be completed by two axial water molecules (not shown).…”

(S)‐(–)‐α,α‐Di(2‐naphthyl)‐2‐pyrrolidinemethanol, a useful tool to study the recognition mechanism in chiral ligand‐exchange chromatography

“…3). In this model, which parallels previously reported examples [2,26,28], the chiral selector is bound to the octadecyl-silica gel through the hydrophobic interaction of the naphthyl groups intercalated between the RP-18 carbon chains of the original stationary phase. Cu(II) is then co-ordinated by the bounded chiral selector and the analyte, thus producing a ternary complex that can be completed by two axial water molecules (not shown).…”

“…24 Relative positive charge surface area: solvent-accessible surface area of the most positive atom divided by descriptor 22 (RPCS). 26 Total hydrophobic surface area: sum of solvent-accessible surface areas of atoms with absolute value of partial charges less than 0.2 (TASA) 27 Total polar surface area: sum of solvent-accessible surface areas of atoms with absolute value of partial charges greater than or equal to 0.2 (TPSA). 28 Relative hydrophobic surface area: total hydrophobic surface area divided by the total molecular solvent-accessible surface area (RASA).…”

“…Both hydrophobically bind to the C-18 carbon chain layer thus producing a stable, dynamically coated chiral stationary phase endowed with good enantiomer recognition ability. Chiral selectors based on amino alcohols received scant attention [11,26]. More recently, Sliwka [27] reported the synthesis and the chromatographic behavior of six N-alkyl-substituted-(S)-phenylglycinol derivatives used as chiral selectors for the HPLC separation of some amino acid enantiomers, thus describing the N-substituent effect and the influence of various factors such as copper(II) ion concentration, mobile phase pH, column temperature and organic modifier addition, on retention, and enantioselectivity.…”

Copper(II) complexes ofN2-alkyl-(S)-amino acid amides as chiral selectors for dynamically coated chiral stationary phases in RP-HPLC

“…Several selectors have been used so far, mostly amino acid derivatives, lPl6 although other optically active materials have also been proposed. [17][18][19] In a systematic approach aimed at studying the mechanism of chiral separation, we developed a series of chiral selectors derived from amino acids, which were able to separate Dnsamino acids, 2o unmodified amino acids, 21 and hydroxy acidsz2 in HPLC with good enantioselectivity factors. Moreover, we have shown that with bis(amino acid amidato)copper(II) complexes added to the eluent, ligand exchange is actually occurring in the chromatographic system, leading to formation of the ternary diastereomeric complexes and displacement of one ligand.…”