Preparative Resolution of Gatifloxacin Enantiomers with Pre-Column Esterification Strategy and Comparing Their Enantioselectivity to Bacteria and Antibody

Gatifloxacin （GFX） is a kind of chiral fluoroquinolones compound due to the methyl group at the C-3 position of the piperazine ring[1]. Although the enantiomers of GFX show similar levels of antimicrobial activity and pharmacokinetics[2], the other biological activities （i.e., toxicity or enantioselective recognition to various receptors in vivo） of GFX enantiomers have not yet been studied. With this in mind, we developed a rapid and cost-effective high performance liquid chromatographic （HPLC） separation procedure for GFX enantiomers with a pre-column esterification strategy.

Equilibrium Studies on Liquid-Liquid Reactive Extraction of Phenylsuccinic Acid Enantiomers Using Hydrophilicβ-CD Derivatives Extractants

This paper deals with the enantioseparation of phenylsuccinic acid(H2A)enantiomers by liquid-liquid reactive extraction usingβ-CD derivatives as aqueous selectors.Cyclodextrin and its derivatives can interact with guest molecules selectively to form complexes with different stabilities.Cyclodextrin derivatives are not soluble in organic liquids,but highly soluble in water.In this work,hydroxypropyl-β-cyclodextrin(HP-β-CD),hydroxyethyl- β-cyclodextrin(HE-β-CD)and methyl-β-cyclodextrin(Me-β-CD)were selected as chiral selectors in aqueous phase for the reactive extraction of phenylsuccinic acid enantiomers from organic phase to aqueous phase.The results show that the efficiency of the extraction depends,often strongly,on a number of process variables,including the types of organic solvents andβ-CD derivatives,the concentrations of the extractants and H2A enantiomers,pH and temperature.HP-β-CD,HE-β-CD and Me-β-CD have stronger recognition abilities for R-phenylsuccinic acid than for S-phenylsuccinic acid.Among the three kinds ofβ-CD derivatives,HP-β-CD has the strongest separation ability. Excellent enantioseparation was achieved under the optimal conditions of pH of 2.5 and temperature of 5°C with a maximum enantioselectivity(a)of 2.38.Reactive extraction of enantiomers with hydrophilicβ-CD derivatives is of strong chiral separation ability and can be hopeful for separations of various enantiomers at a large-scale.

A chiral stationary phase with special hydrophobic framework for ligand-exchange chromatography

A novel chiral stationary phase （CSP1） for ligand-exchange chromatography （CLEC） was prepared by firstly using dimethylchlorosilane as an endcapping reagent for decreasing residual silanol group on the surface of silica gel, and then introducing L-Pro as a chiral selector and hydrophobic octyl group to the silica gel surface simultaneously. The enantioseparations of 14 DL-amino acids on CSP1 were achieved with the enantioselectivity α ranging from 1.09 to 2.44 and the resolution Rs being between 0.8 and 6.3. The chromatographic performances of CSP1 with the bonded phase （CSP2） prepared using reference method were compared. The results showed that the column efficiency and resolution Rs of chiral stationary phase could be improved by using the above modifying method.