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Four macrocyclic glycopeptide chiral stationary phases (CSPs) based on native teicoplanin (Chirobiotic T), methylated teicoplanin aglycone (Chirobiotic m‐TAG), teicoplanin aglycone (Chirobiotic TAG), and vancomycin (Chirobiotic V) were compared for the high performance liquid chromatographic (HPLC) separation of enantiomers of 1‐methyl‐2‐piperidinoethylesters of 2‐, 3‐and 4‐ alkoxyphenylcarbamic acid (potential local anaesthetic drugs). The enthalpies (Δ H i ), entropies (Δ S i ), and Gibbs energies (Δ G i ) of transfer were evaluated for the separation of these compounds. The enantiomers were separated isothermally in the range of 0–50°C with 10°C increments, in the polar organic mode. The thermodynamic parameters were calculated in order to gain an understanding of the driving forces for retention in this chromatographic system. From these results, it is evident that the elongation of the alkoxy‐chain has major influence on the values of (Δ S i ) when using the vancomycin CSP and on the values of (Δ H i ) using the teicoplanin‐type CSPs. [ABSTRACT FROM AUTHOR]

The effect of temperature on the LC resolution of racemic aromatic sulfoxides was studied between 10 and 50°C in the polar organic mode on a teicoplanin aglycone chiral stationary phase (CSP). The set of 10 chiral sulfoxides compounds consisted of 2-,3-,4-toluyl methyl sulfoxides and phenyl methyl sulfoxides with different 2-,3-,4-halogen substituents on the aromatic ring. The van't Hoff plots were constructed to determine the thermodynamic data, and in order to promote an understanding of the mechanism of enantioseparation. The van't Hoff plots (ln k versus 1/T and ln a versus 1/T) were linear for all enantiomers. Plots of ln a versus 1/T afforded thermodynamic parameters, such as the change in enthalpies ?(?H 2,1 ) and the change in entropies ?(?S 2,1 ) for the sulfoxide enantiomers. If ?(?H 2,1 ) and ?(?S 2,1 ) are invariant with temperature, the ?(?G 2,1 ) values can be determined using the Gibbs-Helmholtz equation. The influence of different substituents and their position on the aromatic ring of the sulfoxides on their enantioseparation was correlated to the thermodynamic data. The elution order of the sulfoxide enantiomers does not reverse in the temperature range of 10 to 50°C. All chiral sulfoxides separated on teicoplanin aglycone CSP showed the (S)-(+)-enantiomer eluting first at all temperatures. [ABSTRACT FROM AUTHOR]

The enantioselectivity of native and derivatized cyclodextrin stationary phases and macrocyclic glycopeptides for chiral pterocarpans was evaluated using high performance liquid chromatography (HPLC). All enantiomers could be baseline resolved in the reverse phase mode on cyclodextrin-based Cyclobond chiral stationary phases (CSPs). The hydroxypropyl-β-cyclodextrin, acetyl-β-cyclodextrin, and gamma-cyclodextrin CSPs show the broadest enantioselectivity in the reverse phase mode. Some compounds were baseline separated on the ristocetin A and vancomycin macrocyclic glycopeptide chiral stationary phases in the reverse phase mode. Separations on the ristocetin A columns produced the highest resolutions (up to ∼7.1) in this study. The 3,5-dimethylphenyl carbamate derivatized cyclodextrin column showed the broadest enantioselectivity in normal phase LC. Of the macrocyclic glycopeptide CSPs, ristocetin A and teicoplanin aglycone (Chirobiotic R and TAG, respectively) showed enantioselectivity for the most compounds in the normal phase mode. However, baseline separations were only achieved with the teicoplanin and teicoplanin aglycone. [ABSTRACT FROM AUTHOR]

The enantiomers of 1-methyl-2-piperidinoethylesters of 3- and 4-alkoxyphenylcarbamic acid were separated on vancomycin(CHIROBIOTIC V) and teicoplanin(CHIROBIOTIC T) columns isothermally in the range of 0–50°C at 10°C increments, using methanol containing 17.5 mmol/L acetic acid and 4.8 mmol/L diethylamine as the mobile phase. Lower temperatures produced the expected increase in retention of the studied enantiomers and improved their separation. The retention factors ki(as well as the resolutions Rij) were higher on the teicoplanin chiral stationary phase(CSP) compared with the vancomycin CSP. Van't Hoff plots(dependence of ln ki on 1/T) were linear within the temperature interval studied, and they also were used to determine thermodynamic data, such as the(ΔHi) and(ΔSi) of transfer of the enantiomers between mobile and stationary phases. From these results, it is evident that the prolongation of carbon atoms in the alkoxy-chain has a major influence on the values ofΔ(ΔS2,1) using the vancomycin CSP, and on the values ofΔ(ΔH2,1) using the teicoplanin CSP. However, when the alkoxy-substituent on the phenylcarbamic acid ring system is in the 3- and 4-positions, there seems to be little difference in the thermodynamic parameters. [ABSTRACT FROM AUTHOR]