Evaluation and comparison of a methylated teicoplanin aglycone to teicoplanin aglycone and natural teicoplanin chiral stationary phases

Abstract

HPLC enantiomeric separations of a wide variety of racemic analytes was evaluated using chiral stationary phases (CSPs) based on the macrocyclic glycopeptides teicoplanin (T), teicoplanin aglycone (TAG), and methylated teicoplanin aglycone (Me-TAG) in two different mobile phase modes, i.e., the RP mode and the polar organic (PO) mode. Comparison of the enantiomeric separations using Chirobiotic T, Chirobiotic TAG, and the methylated form of TAG were conducted in order to gain a better understanding of the roles of the polar functional groups on the CSP. Substantial effects due to the cleavage of saccharides and/or methylation on chiral separations were observed in both separation modes. Improved separation efficiencies for many acidic analytes were obtained by methylating the H-bonding groups of TAG. These groups were believed to be a contributing factor to band broadening on TAG due to their negative effect on mass transfer between the stationary phase and mobile phase. Ionic/dipolar interactions between the carboxylate group of the analytes and the amine groups on T, TAG, or Me-TAG are important for chiral discrimination. Therefore, analytes possessing a carboxyl group are good candidates for successful separations on these CSPs. Hydrophobic interactions are important for enantiomeric separations in the RP mode where the H-bonding interactions between analytes and the chiral selectors are relatively weak. Me-TAG offers higher hydrophobicity, which can accentuate the interactions of analytes with hydrophobic moieties, but these interactions are not necessarily stereoselective. In the PO mobile phase, electrostatic/dipolar interactions between polar functional groups are the dominating interactions in chiral recognition. Another important factor is steric fit, which could be changed with every modification of the T structure. Therefore, substantial changes of enantioseparations were obtained within this studied group of CSPs. The PO mode was shown to be the most powerful mobile phase mode for enantiomeric separations on T-based stationary phases, mainly due to the improved efficiency. Methylation of the TAG proved to be a very useful tool for investigating the chiral recognition mechanism for this group of chiral selectors.

Chiral recognition mechanisms with macrocyclic glycopeptide selectors

“…They were only 0.59 and 0.60 with a TAG column and the same mobile phase. 20 Similar results were obtained with the vancomycin selector. However, the vancomycin aglycon CSP was never commercialized because it had a reduced application spectrum compared to the TAG CSP.…”

“…The b-blocker drugs were much better separated on teicoplanin CSP in PIM than on TAG CSP. 20 For example, acebutolol was separated with a resolution factor of 2.16 with a teicopanin column and not (Rs 5 0) with a TAG column. The resolution factor for propranolol and atenolol were 2.78 and 2.16, respectively, with a teicoplanin column and a PIM mobile phase.…”

Evaluation and Comparison of a 3,5‐Dimethylphenyl Isocyanate Teicoplanin with Phenyl Isocyanate Teicoplanin Chiral Stationary Phase Using RP‐HPLC

“…The 3,5-dimethylphenylisocyanate derivative of vancomycin was made and tested as a CSP. [2] Removal of carbohydrate (sugar) moieties from native teicoplanin, [14] methylated teicoplanin aglycone (Me-TAG) [15] produced two new kinds of chiral selector which were from native teicoplanin.…”

Enantiomer elválasztás és felismerés nagyhatékonyságú folyadékkromatográfiás rendszerekben

“…Savas karakterű vegyületek enantimerjeinek elválasztására a hidroxilcsoportok metilezésével próbálták 17 specifikusabbá tenni a teikoplanin aglikont [43]. …”