title: Resolution and isolation of enantiomers of (±)-isoxsuprine using thin silica gel layers impregnated with L-glutamic acid, comparison of separation of its diastereomers prepared with chiral derivatizing reagents having L-amino acids as chiral auxiliaries.
abstract: Thin silica gel layers impregnated with optically pure l-glutamic acid were used for direct resolution of enantiomers of (±)-isoxsuprine in their native form. Three chiral derivatizing reagents, based on DFDNB moiety, were synthesized having l-alanine, l-valine and S-benzyl-l-cysteine as chiral auxiliaries. These were used to prepare diastereomers under microwave irradiation and conventional heating. The diastereomers were separated by reversed-phase high-performance liquid chromatography on a C18 column with detection at 340 nm using gradient elution with mobile phase containing aqueous trifluoroacetic acid and acetonitrile in different compositions and by thin-layer chromatography (TLC) on reversed phase (RP) C18 plates. Diastereomers prepared with enantiomerically pure (+)-isoxsuprine were used as standards for the determination of the elution order of diastereomers of (±)-isoxsuprine. The elution order in the experimental study of RP-TLC and RP-HPLC supported the developed optimized structures of diastereomers based on density functional theory. The limit of detection was 0.1-0.09 µg/mL in TLC while it was in the range of 22-23 pg/mL in HPLC and 11-13 ng/mL in RP-TLC for each enantiomer. The conditions of derivatization and chromatographic separation were optimized. The method was validated for accuracy, precision, limit of detection and limit of quantification.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, 247667, India.
authors.forename: Ravi
authors.initials: R
authors.lastname: Bhushan
authors.forename: Hariom
authors.initials: H
authors.lastname: Nagar
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D056148:Chromatography, Reverse-Phase / Q000379:methods*; D002855:Chromatography, Thin Layer / Q000295:instrumentation / Q000379:methods*; D018698:Glutamic Acid / Q000737:chemistry*; D007556:Isoxsuprine / Q000737:chemistry* / Q000302:isolation & purification*; D057230:Limit of Detection; D015394:Molecular Structure; D015203:Reproducibility of Results; D058428:Silica Gel; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D018698:Glutamic Acid; D058428:Silica Gel; D007556:Isoxsuprine
keywords: (±)-isoxsuprine; chiral derivatizing reagent; enantioresolution; impregnated thin-layer chromatography; reversed-phase high-performance liquid chromatography