A liquid chromatographic chiral stationary phase based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 covalently bonded to silica gel was applied in the resolution of aryl alpha-amino ketones including cathinone, the main psychoactive alkaloid found in the leaves of the khat plant. The resolution was excellent, the separation factors ranging between 1.72 and 8.58 and the resolution factors (R(S)) ranging between 2.60 and 11.10. The chromatographic resolution behaviour was dependent on the type and the content of organic and acidic modifiers and the ammonium acetate concentration in aqueous mobile phase and the column temperature.
A chiral stationary phase (CSP 1) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was applied to the resolution of N-(substituted benzoyl)-alpha-amino acid amides and esters. N-(Substituted benzoyl)-alpha-amino acid amides were well resolved using a mixture of acetic acid-triethylamine-acetonitrile (0.01:0.05:100, v/v/v) as an optimum mobile phase while N-(substituted benzoyl)-alpha-amino acid esters were not resolved at all. In contrast, both N-(substituted benzoyl)-alpha-amino acid amides and esters were not resolved at all or resolved very poorly on another CSP (CSP 2), which lacks the two N-H hydrogens of the amide tethers of CSP 1. Among the substituents on the benzoyl group of analytes, the nitro group was the best for good resolution of analytes on CSP 1. From these results, the two N-H hydrogens of the amide tethers of CSP 1, the carbonyl oxygen of the amide group of analytes, and the nitro group on the benzoyl group of analytes were concluded to play significant roles in chiral recognition. In addition, various N-(3,5-dinitrobenzoyl)leucine amides with different lengths of N-alkylamide chains were resolved on CSP 1 and N-(3,5-dinitrobenzoyl) leucine N-propylamide was found to show the best chiral recognition in terms of the separation (alpha = 1.30) and the resolution factor (Rs= 3.17).
To identify the compounds absorbed in rat serum after the oral administration of Wu-Jia Sheng-Hua (WJSH) capsule, a traditional Chinese medicine (TCM) compound prescription, an ultraperformance liquid chromatography coupled with electrospray ionization mass spectrometry (UPLC/ESI-MS) method, was established. The chromatographic separation of the absorbed compounds and metabolites was achieved with an ACQUITY UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm) under a gradient elution. The mobile phase was composed of acetonitrile and water buffered with ammonium acetate (10 mM) and formic acid (0.1%, V/V). Twelve absorbed compounds and four metabolites were found. Seven of the absorbed compounds were identified by ESI-MS. The identification of absorbed compounds might be helpful for the better understanding of the mechanisms underlying the pharmacological effects of WJSH capsule.
A facile methodology for synthesis of bicyclopeptides containing isoindolone was developed by intramolecularly photo-induced electron transfer cyclo-reaction (IPETC) with high yield and stereoselectivity. Nine bisulfide-bridged bisisodindolone-cyclopeptides were successfully prepared based...
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