Enantioseparation using urea‐ and imide‐bearing chitosan phenylcarbamate derivatives as chiral stationary phases for high‐performance liquid chromatography

Abstract

Completely deacetylated chitosan was prepared by the treatment of commercial chitosan with 50% aqueous NaOH, and then derivatized into several new chitosan phenylcarbamate derivatives having a urea and an imide moiety at the 2-position of the glucosamine ring by the reaction with isocyanate and phthalic anhydride/isocyanate, respectively. The chitosan derivatives were coated on macroporous silica gel and evaluated as chiral stationary phases (CSPs) for high-performance liquid chromatography. The chiral recognition ability of the chitosan derivative was improved using the completely deacetylated chitosan. Among the novel chitosan derivatives, the 3,5-dimethyl-, 3,5-dichloro-, and 3,4-dichlorophenylcarbamate derivatives were found to possess relatively high chiral resolution abilities. The CSPs based on the chitosan phenylcarbamate-urea and -imide derivatives were stable in the presence of chloroform and ethyl acetate as a component of the eluents, and some racemates were better resolved by such eluents. The dichlorophenylcarbamate-imide derivatives showed a high chiral recognition for metal acetylacetonate complexes. The enantiomerization of Al(acac)3 was performed on the chitosan 3,5-dichlorophenylcarbamate-imide derivative CSP and the resulting chromatogram showed a 26% (+)-isomer enrichment.

Chiral stationary phases based on chitosan bis(methylphenylcarbamate)-(isobutyrylamide) for high-performance liquid chromatography

“…The similar trends could also be found for the chitosan derivatives [22,25]. As shown in Table 1 and Figs.…”

“…The lower solubility of chiral selectors is very important for the coated-type CSPs of polysaccharide derivatives, because these CSPs can work in a wider range of mobile phases, in which better enantioseparations may be gained. To date, there is still only a few studies and much less attention has been paid on chitosan derivatives based CSPs [23][24][25][26][27][28][29][30][31]. Meanwhile, most of the common coated-type CSPs exhibited poor solvent resistance in some organic solvents.…”

Enantioseparation Using Chitosan Tris(3-chlorophenylcarbamate) as a Chiral Stationary Phase for HPLC

“…Therefore, it has been used as a starting material in the preparation of chiral selectors [5][6][7][8][9]. In 2008, Yamamoto et al [10] synthesized chitosan-urea and -imide phenylcarbamate derivatives and coated them onto a 7 lm macroporous silica gel pretreated with 3-aminopropyltriethoxysilane. It is interesting to note that these chitosan derivatives exhibited optical resolutions that were equal to or higher than those of cellulose or amylose derivatives.…”

Studies of the Interesting Gas‐phase Rearrangement Reactions of 2‐Pyrimidinyloxy‐N‐arylbenzylurea Promoted by Urea‐Carbamimidic Acid Tautomerism by ESI‐MS/MS and Theoretical Computation

“…All optimized structures were subjected to vibrational frequency analysis. 6,19 The optimized structures were shown by software Gauss View (3.07).…”

“…With the development of lift science and diversification of research methods, the gas-phase chemistry about the compounds containing urea group is becoming a very attractive field. [4][5][6] Electrospray ionization tandem mass spectrometry (ESI-MS/MS) with both positive and negative ion modes, 7 as the ionization technology, was applied to investigating the gas-phase chemistries of compound 1, by transferring the preformed ions directly from solution to the gas-phase and studying its unimolecular transformations in the solvent-free conditions. 8 Our studies showed some general gas-phase chemistries of 2-pyrimidinyloxy-N-arylbenzylamines, such as intramolecular S N 2 reaction and Smiles rearrangement processes reported previously.…”