18-crown-6-2-3-11-12-tetracarboxylic-acid and triethylamine

Fendiline, an effective anti-anginal drug for the treatment of coronary heart diseases, and its sixteen analogues were resolved on a CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid. Fendiline was resolved quite well with the separation factor (α) of 1.25 and resolution (RS) of 1.55 when a mobile phase consisting of methanol-acetonitrile-trifluoroacetic acid-triethylamine at a ratio of 80/20/0.1/0.5 (v/v/v/v) was used. The comparison of the chromatographic behaviors for the resolution of fendiline and its analogues indicated that the 3,3-diphenylpropyl group bonded to the secondary amino group of fendiline is important in the chiral recognition and the difference in the steric bulkiness between the phenyl group and the methyl group at the chiral center of fendiline is also important in the chiral recognition.

Topics: Acetonitriles; Cardiovascular Agents; Chromatography, Liquid; Crown Ethers; Ethylamines; Fendiline; Methanol; Solvents; Trifluoroacetic Acid

A liquid chromatographic chiral stationary phase (CSP) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was applied for the first time to the resolution of biologically important 1-aryl-1,2,3,4-tetrahydroisoquinolines. The unusual resolution of cyclic secondary amino compounds on a chiral crown ether-based CSP was quite successful with the use of a mixture of methanol-acetonitrile-triethylamine at a ratio of 30/70/0.5 (v/v/v) as a mobile phase. From the chromatographic behaviours for the resolution of seven 1-aryl-1,2,3,4-tetrahydroisoquinolines, the steric bulkiness of the 1-phenyl ring at the chiral center of analytes was concluded to play an important role in the chiral recognition.

Topics: Acetonitriles; Chromatography, Liquid; Crown Ethers; Ethylamines; Methanol; Stereoisomerism; Tetrahydroisoquinolines

Chiral differentiation of four enantiomeric pairs of beta-amino acids, cis-(1R,2S)-, cis-(1S,2R)-, trans-(1R,2R)-, and trans-(1S,2S)-2-aminocyclopentanecarboxylic acids (cyclopentane beta-amino acids), and cis-(1R,2S)-, cis-(1S,2R)-, trans-(1R,2R)-, and trans-(1S,2S)-2-aminocyclohexanecarboxylic acids (cyclohexane beta-amino acids) was performed successfully by using host-guest complexes and ion/molecule reactions. The experiments were conducted by using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The effect of a chiral host molecule was tested by using three different host compounds; (+)-(18-Crown-6)-2,3,11,12-tetracarboxylic acid, (-)-(18-Crown-6)-2,3,11,12-tetracarboxylic acid, and beta-cyclodextrin. This is the first time that small enantiomeric pairs with two chiral centers have been differentiated using ion/molecule reactions and host-guest complexes.

Topics: Amino Acids; beta-Cyclodextrins; Crown Ethers; Cyclohexanes; Cyclopentanes; Ethylamines; Spectrometry, Mass, Electrospray Ionization; Spectroscopy, Fourier Transform Infrared; Stereoisomerism

While HPLC chiral stationary phases (CSPs) based on chiral crown ethers have been known useful for the resolution of only racemic primary amino compounds or some secondary amino compounds, in this study, we first demonstrated that the CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid is also useful for the resolution of N-benzoyl-alpha-amino acids, which do not contain a primary or secondary amino group. Especially, N-(3,5-dinitrobenzoyl)-alpha-amino acids were resolved better than corresponding N-(3-nitrobenzoyl)- or N-benzoyl-alpha-amino acids, the separation (alpha) and the resolution factors (R(S)) for the resolution of eight N-(3,5-dinitrobenzoyl)-alpha-amino acids being in the range of 1.06-1.81 and 0.54-2.81, respectively. The optimum mobile phase condition was the mixture of acetic acid-triethylamine-acetonitrile with the ratio of 0.05/0.25/100 (v/v/v).

Topics: Acetic Acid; Acetonitriles; Amino Acids; Chromatography, High Pressure Liquid; Crown Ethers; Ethylamines; Molecular Structure; Nitrobenzoates; Reproducibility of Results

Recently, a new HPLC chiral stationary phase (CSP) prepared by covalently bonding (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid on silica gel was successfully employed in resolving various racemic natural and unnatural amino acids containing a primary amino group. Current work details on-going efforts to improve the effectiveness of this type of material. The analytes used in this study included various substituted phenylalanines, phenylglycine homologues and other primary amino acids. In an attempt to increase enantioselectivity, the effect of methanol and triethylamine modifiers was evaluated in an aqueous mobile phase containing sulfuric acid. In general. retention time increased with increasing methanol and triethylamine concentration. In addition, highest enantioselectivities were obtained with high methanol and high triethylamine; however, these conditions produced excessively long retention. All of the analytes were well resolved on the CSP with a mobile phase of 20% methanol containing 14.3 mM triethylamine and 10.0 mM sulfuric acid.

Topics: Amino Acids; Chromatography, High Pressure Liquid; Crown Ethers; Ethers, Cyclic; Ethylamines; Stereoisomerism