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  • Author or Editor: Manisha Singh x
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Direct enantioseparation of (±)-terbutaline has been achieved by ligand-exchange thin-layer chromatography. Enantiomerically pure L-amino acids (namely, L-tryptophan, L-phenyl alanine, and L-histidine) and Cu(II) acetate were used for the preparation of ligand- exchange reagents. Three different approaches were adopted for impregnating the plate with ligand-exchange reagents. The solvent system MeCN–CH2Cl2–MeOH–H2O, in different proportions, was found to be successful for enantioseparation. The results obtained with all the approaches have been compared. The effect of the concentration of Cu(II) acetate and a chiral selector has also been investigated. The spots were located in an iodine chamber.

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Abstract  

Hydrogen sulphate, nitrate and perchlorate salts of diphenylamine have been prepared and characterized by elemental, spectral and gravimetric analyses. Thermal decomposition of these salts has been evaluated by TG (static air) and DSC (inert atmosphere). The proton transfer reaction plays a major role during thermolysis of these salts. The diphenylammonium hydrogen sulphate under thermal and microwave irradiation forms 4-(phenylamino) benzenesulphonic acid by sulphonation process, whereas nitrate and perchlorate salts do not form corresponding nitro and perchloro derivatives, rather they ignite and explode, respectively, to form gaseous products along with a residual carbon .

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The present paper deals with direct enantioresolution of (±)-bupropion using thin-layer chromatography and different Cu(II)-l-amino acid complexes as chiral ligand exchange reagent (LER). Cu(II) acetate and four l-amino acids (viz., l-proline, l-histidine, l-phenylalanine, and l-tryptophan) were used for the preparation of LER. Four different approaches were adopted for impregnating/loading the plate with the LER. In the present work, plate impregnation was achieved (a) by mixing LER with silica gel slurry, (b) by developing plain plates with solutions of the Cu complexes, (c) using a solution of Cu(II) acetate as mobile phase additive for the thin-layer chromatography (TLC) plates impregnated with one of the l-amino acids, and (d) by using the LER as mobile phase additive. Spots were located using iodine vapor. The results obtained with all the approaches have been compared in terms of resolution. Effect of concentration of Cu(II) acetate and chiral selector has also been studied.

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Direct enantioresolution of (±)-etodolac has been achieved by adopting a new conceptual approach involving both achiral phases in thin-layer chromatography (TLC). Enantiomerically pure l-tryptophan, l-phenyl alanine, l-histidine, and l-arginine were used as chiral inducing reagents (CIR); none of these was impregnated with silica gel (while making TLC plates) or mixed with the mobile phase. The solvent system MeCN—CH2Cl2—MeOH, in different proportions, was found to be successful for enantioresolution. Spots were located in iodine chamber. Effect of concentration of chiral inducing reagent and temperature on enantioresolution was studied.

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Summary

Direct resolution of enantiomers of (RS)-ketorolac was achieved by thin-layer chromatography on silica gel plates using enantiomerically pure L-tryptophan, L-valine, L-methionine, and L-histidine as chiral additive in the stationary phase. The solvent system (acetonitrile, methanol water, and chloroform) with different ratios was successful in resolving the enantiomers. Spots were detected by use of iodine vapor. The detection limit was 0.4 µg mL−1 for each enantiomer of (RS)-ketorolac. The native enantiomers were isolated and characterized.

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