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Cyclodextrins that are indiscriminately carboxymethylated at the 2‐, 3‐, and 6‐positions are used as chiral NMR solvating agents for cationic substrates with phenyl, naphthyl, pyridyl, indoline, and indole rings. Enantiodifferentiation with the α‐, β‐, and γ‐cyclodextrin derivatives is compared. The carboxymethylated derivatives are almost always more effective as chiral NMR solvating agents for cationic...
The application of (S)‐1,1′‐binaphthyl‐2,2′‐diol as NMR chiral solvating agent (CSA) for omeprazole, and three of its analogs (lanso‐, panto‐, and rabe‐prazole) was investigated. The formation of diastereomeric host–guest complexes in solution between the CSA and the racemic substrates produced sufficient NMR signal splitting for the determination of enantiomeric excesses by 1H‐ or 19F‐NMR spectroscopy...
A sulfonated calix[4]resorcinarene containing L‐pipecolinic acid groups is investigated as a water‐soluble chiral NMR solvating agent. Aromatic substrates with phenyl, indole, indane, naphthyl, and pyridyl rings are analyzed. The substrates, which are water soluble because of ammonium, hydroxyl, or carboxylate functional groups, form host–guest complexes by insertion of the aromatic ring into the...
(R)‐(−)‐α‐Methoxy phenyl acetic acid, (S)‐(−)‐1,1′‐(2‐naphthol), and (R)‐(+)‐α‐methoxy‐α‐trifluoromethyl phenyl acetic acid were evaluated as chiral shift reagents (CSRs) for 1H NMR spectroscopic resolution and determination of R and S enantiomers of modafinil (MDL) in bulk drugs and formulations. Effects of the nature of CSR and the weight ratio of substrate to shift reagent on enantiomeric discrimination...
A simple, sensitive, and robust normal‐phase isocratic HPLC‐UV method was developed and validated for the enantiomeric separation of rasagiline mesylate and its (S)‐enantiomer. The rasagiline and its (S)‐enantiomer were resolved on a Chiralcel‐OJ‐H (4‐methylbenzoate cellulose coated on silica) column using a mobile phase consisting of n‐hexane:isopropyl alcohol:ethanol:diethyl amine (96:2:2:0.01)...
A sensitive and specific method for the simultaneous determination of the enantiomeric purity of 2,6‐dimethylphenoxyacetyl derivatives as trans or cis racemic and enantiomeric forms with 2‐ or 4‐aminocyclohexanol moiety (1, 2, 3, 6) and their amine analogs (8, 9) was developed. The compounds studied are known for their anticonvulsant activity and the most interesting pharmacological results were those...
The observation of nonequivalence of optical and enantiomeric purities, referred to as the Horeau effect, is thought to arise from molecular aggregation in liquid solutions. Although this effect was first observed in 1969, the conditions under which this effect may, or may not, be observable are not established. Considering the formation of dimers as the simplest form of aggregation, the expressions...
The use of ortho‐phthalaldehyde (OPA) for the derivatization of amino acids (AA) is well known. It enables the separation of the derivatives on common reversed phase columns and improves the sensitivity with fluorescence detection. With the use of a chiral thiol an indirect enantioseparation of chiral amines and AAs is feasible. The major drawback of the OPA‐derivatization is the poor stability of...
The enantioresolution and determination of the enantiomeric purity of 32 new xanthone derivatives, synthesized in enantiomerically pure form, were investigated on (S,S)‐Whelk‐O1 chiral stationary phase (CSP). Enantioselectivity and resolution (α and RS) with values ranging from 1.41–6.25 and from 1.29–17.20, respectively, were achieved. The elution was in polar organic mode with acetonitrile/methanol...
Stereospecific separation method of (±) betaxolol, (±) carvedilol, and (±) sotalol using High Performance Thin Layer Chromatography (HPTLC) and β‐cyclodextrin as chiral selector has been developed and validated. The Box‐Behnken surface response design was selected for optimizing the operating variables based on 15 trials design. The optimized method involves separation on Fluka HPTLC silica gel plates...
Vilanterol trifenatate is a novel chiral long‐acting β2‐agonist developed. Vilanterol combined with inhaled corticosteroids can treat COPD and asthma. A simple liquid chromatographic method is developed for the quantitative determination of R‐vilanterol and S‐vilanterol (impurity S). HPLC separation was achieved on Chiralpak ID (250 × 4.6 mm; particle size 5 μm) column using hexane‐ethanol‐ethanolamine...
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