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Stereoselective high‐performance liquid chromatographic and subcritical fluid chromatographic separations of 19 Nα‐Fmoc proteinogenic amino acid enantiomers were carried out by using Quinidine‐based zwitterionic and anion‐exchanger‐type chiral stationary phases Chiralpak ZWIX(−) and QD‐AX. For optimization of retention and enantioselectivity, the ratio of bulk solvent components (MeOH/MeCN, H2O/MeOH,...
The compound (18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid was evaluated as a chiral nuclear magnetic resonance (NMR) solvating agent for a series of diamines and bicyclic β‐amino acids. The amine must be protonated for strong association with the crown ether. An advantage of (18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid over many other crown ethers is that it undergoes a neutralization reaction with...
Stereoselective high‐performance liquid chromatographic separations of eight sterically constrained cyclic β‐amino acid enantiomer pairs were carried out using the newly developed Cinchona alkaloid‐based zwitterionic chiral stationary phases Chiralpak ZWIX(+) and ZWIX(−). The effects of the mobile phase composition, the nature and concentrations of the acid and base additives, the counterions and...
The effects of temperature on the chiral recognition of cyclic β‐amino acid enantiomers on zwitterionic [Chiralpak ZWIX(+) and ZWIX(–)] chiral stationary phases were investigated. Experiments were performed at different mobile phase compositions and under 10°C column temperature increments in the temperature range 10–50°C. Apparent thermodynamic parameters and Tiso values were calculated from plots...
Direct high‐performance liquid chromatographic (HPLC) separation of four bicyclo[2.2.2]octane based 2‐amino‐3‐carboxylic acid enantiomers were developed on chiral stationary phases (CSPs) containing different macrocyclic glycopeptide antibiotic selectors. The analyses were performed under reversed‐phase, polar organic and polar ionic mode on macrocyclic‐glycopeptide‐based Chirobiotic T, T2, TAG, and...
(18‐Crown‐6)‐2,3,11,12‐tetracarboxylic acid is a useful chiral NMR solvating agent for isoxazoline‐fused β‐amino acid derivatives. Isoxazoline substrates are analyzed as their hydrochloride salts in methanol‐d4. The crown ether and substrate associate through the formation of three hydrogen bonds between the protonated amine and crown ether oxygen atoms. Enantiomeric discrimination is observed for...
The enantiomers of four unusual isoxazoline‐fused 2‐aminocyclopentanecarboxylic acids were directly separated on chiral stationary phases containing (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid as chiral selector. The nature of the alcoholic modifier (MeOH, EtOH, IPA) exerted a great effect on the retention, whereas the selectivity and resolution did not change substantially. Two types of dependence...
The direct separation of the enantiomers of 1‐(α‐aminoarylmethyl)‐2‐naphthol, 1‐(α‐aminoalkyl)‐2‐naphthol, 2‐(α‐aminoarylmethyl)‐1‐naphthol analogs, and 2‐(1‐amino‐2‐methylpropyl)‐1‐naphthol) was performed on a newly developed chiral stationary phase containing isopropyl carbamate‐cyclofructan6 as chiral selector, with n‐heptane/alcohol/trifluoroacetic acid as mobile phase. The effects of the mobile‐phase...
High‐performance liquid chromatographic methods were developed for the separation of the enantiomers of 19 β‐lactams. The direct separations were performed on chiral stationary phases containing either amylose‐tris‐3,5‐dimethylphenyl carbamate, (Kromasil® AmyCoat™ column) or cellulose‐tris‐3,5‐dimethylphenyl carbamate, (Kromasil® CelluCoat™ column) as chiral selector. The different methods were compared...
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