The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The enantioselective degradation of tebuconazole has been investigated to elucidate the behaviors in agricultural soils, cabbage, and cucumber fruit. Rac‐tebuconazole was fortified into three types of agricultural soils and sprayed foliage of cabbage and cucumber, respectively. The degradation kinetics, enantiomer fraction and enantiomeric selectivity were determined by reverse‐phase high‐performance...
The chiral discrimination mechanism in the resolution of sertraline with mandelic acid was investigated by examining the weak intermolecular interactions (such as hydrogen bond, CH/π, and van der Waals interactions) and molecular packing difference in crystal structures of the resulting diastereomeric salts. A new one‐dimensional chain‐like hydrogen‐bonding network and unique supramolecular packing...
Ionic liquids (ILs) have been widely used as reaction solvents in asymmetric synthesis due to their interesting physical and chemical properties. However, monitoring reactant‐to‐product conversion and the enantiopurity of formed stereoisomers often involves a tedious extraction step before chromatographic analysis. In this study, a rapid and sensitive sampling method using headspace solid‐phase microextraction...
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...
The synthesis of planar chiral strong Brønsted acid organocatalysts derived from [2.2]paracyclophane is described. Resolution was accomplished according to a modified protocol involving pseudo‐ortho‐substituted [2.2]paracyclophane‐based sulfoxides for the synthesis of three new sulfonic acids. The first planar chiral phosphoric acid diester was obtained from the corresponding phenyl‐substituted diol...
5,6‐Dihydro‐1,10‐phenanthrolines can display axial and central chirality. In conjunction with the ligating properties of the diimino moiety, this class of compounds is of great interest to applications in supramolecular chemistry. We report the first preparation of cis‐5,6‐dihydro‐1,10‐phenanthroline derivatives by reacting triphenyl borate with the corresponding epoxide precursor. We found that solvent...
Tetrahydroberberine (THB), a racemic mixture of (+)‐ and (−)‐enantiomer, is a biologically active ingredient isolated from a traditional Chinese herb Rhizoma corydalis (yanhusuo). A chiral high performance liquid chromatography method has been developed for the determination of THB enantiomers in rat plasma. The enantioseparation was carried out on a Chiral®‐AD column using methanol:ethanol (80:20,...
The screening of the catalytic activity in the diethylzinc reaction of a series of easily accessible (1S)‐ketopinic‐acid derived hydroxyamides, designed by key structure modifications of a parent highly active related bis(hydroxyamide), has allowed to find the first case of dual stereoselection in highly structurally close ligands of such interesting chemically sustainable typology. The found striking...
A cinchona alkaloid‐derived thiourea catalyst has been designed to access new asymmetric β‐amino esters bearing benzothiazole moiety by utilizing a Mannich reaction between an imine and a malonate. A simultaneous activation of the two imine functionalities and malonate by the bifunctional chiral organocatalyst is proposed to account for the good yields (71–91%) and high enantiomeric excess (89.4–98...
A cyclodextrin‐modified micellar electrokinetic chromatography (CD‐MEKC) technique has been developed for enantioseparation of vinpocetine using an inexpensive 2‐hydroxypropyl‐β‐CD (HP‐β‐CD) as the chiral selector (CS). The best chiral separation was achieved using 40 mM HP‐β‐CD as the CS in 50 mM phosphate buffer (pH 7.0) consisting of 40 mM sodium dodecyl sulfate (SDS) at a separation temperature...
Carvedilol is an antihypertensive drug available as a racemic mixture. (−)‐(S)‐carvedilol is responsible for the nonselective β‐blocker activity but both enantiomers present similar activity on α1‐adrenergic receptor. To our knowledge, this is the first study of carvedilol enantiomers in human plasma using a chiral stationary phase column and liquid chromatography with tandem mass spectrometry. The...
A series of chiral pyrrolidine‐sulfamides were prepared and examined as the catalysts for conjugate addition of ketones to nitroalkenes. Benzoic acid was identified as the most efficient additives for the transformation. Excellent enantioselectivities, diastereoselectivities, and yields were achieved for the reaction of cyclohexanone with β‐aryl nitroethylenes under solvent free conditions. β‐Isopropyl...
A protocol was developed for the solution‐phase synthesis of multigram amounts of two 9‐fluorenylmethoxycarbonyl (Fmoc)‐protected tetraproline peptides. These tetraproline peptides were then attached to amino derivatized silica gel. The replacement of the Fmoc group with the trimethylacetyl group lead to two tetraproline chiral stationary phases (CSPs). A comparison of the chromatographic behavior...
A chiral capillary electrophoresis method has been developed for the quantification of 0.1% of the enantiomeric impurity (dextrocetirizine) in levocetirizine and determination of both in pharmaceuticals using sulfated‐β‐cyclodextrins (CDs) as chiral selector. Several parameters affecting the separation were studied such as the type and concentration of chiral selectors, buffer composition and pH,...
Hexaconazole [(RS)‐2‐(2,4‐dichlorophenyl)‐1‐(1H‐1,2,4‐triazol‐1‐yl) hexan‐2‐ol] is a potent triazole fungicide and consists of a pair of enantiomers. Enantioselective degradation of hexaconazole was investigated in rat hepatic microsomes in vitro. Concentrations of (−)‐ and (+)‐hexaconazole and enantiomer fraction were determined by high performance liquid chromatography with a cellulose‐tris‐(3,5‐dimethylphenylcarbamate)‐based...
Nine novel (+)‐camphor‐derived thioureas have been prepared. 3‐((Dimethylamino)methylene)camphor (2) served as the common precursor for the preparation of both, 2‐thiourea 15, 16, 17, 18, 19, 20 and 3‐thiourea functionalized camphor derivatives 6, 7/7', respectively. Starting from 2, the latter were prepared in two or three steps whereas the former in five steps, respectively. Configuration of all...
(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...
Several pyrrolidine–camphor derived organocatalysts were designed and synthesized. These organocatalysts were used for direct Michael reaction of aldehydes with nitroalkenes to give the desired γ‐nitrocarbonyl compounds in high yields (up to 99%), high diastereoselectivities (syn:anti up to 92:8), and good to excellent enantioselectivities (up to 94% ee). Possible transition‐state model was also proposed...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.