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Enantioseparation and estimation of racemization barriers of selected helquats and their derivatives by capillary electrophoresis using sulfated cyclodextrins as chiral selectors
Sázelová, Petra ; Koval, Dušan ; Severa, Lukáš ; Reyes Gutierrez, Paul Eduardo ; Jirásek, Michael ; Teplý, Filip ; Kašička, Václav
Anionic highly sulfated β- and γ-cyclodextrins (S-CDs) and single-isomer heptakis-(2,3-diacetyl-6-sulfato)-β-CD (14Ac-7S-β-CD) were used for chiral separation of [5], [6] and [7]-ring helquats and helquat styryl dyes by capillary electrophoresis (CE) in the background electrolyte composed of 22 mM NaOH/35 mM H3PO4, pH 2.4. The CE method was applied for monitoring of racemization of eight helquats and helical dyes. Rate constant k of conversion, half-life T1/2 of racemization, and activation Gibbs free energy ΔGǂ of interconversion of one enantiomer into the other were calculated from the dependence of natural logarithm of enantiomeric excess (ee) on time using linear regression analysis.
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Capillary electrophoresis applied to chiral analysis of helquats and characterization of their intermediates and interconversion barriers using randomly and single isomer sulfated cyclodextrins as stereoselectors
Kašička, Václav ; Koval, Dušan ; Sázelová, Petra ; Severa, Lukáš ; Vávra, Jan ; Adriaenssens, Louis ; Sonawane, Manoj R. ; Teplý, Filip
Capillary electrophoresis in acidic sodium phosphate background electrolyte, pH 2.4, with randomly sulfated alfa-, beta- and gamma-cyclodextrins as chiral selectors was applied to fast, high-resolution separation of enantiomers of a series of 35 helquats, a new class of N-heteroaromatic dicationic helicene-like species. The developed methodology was employed for evaluation of preparative enantioresolution procedures of helquats, for monitoring their racemization and for determination of interconversion barrier of helquat enantiomers.
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Enantiomer separation and determination of helix inversion barrier of helical dications by capillary electrophoresis
Koval, Dušan ; Adriaenssens, Louis ; Severa, Lukáš ; Teplý, Filip ; Sázelová, Petra ; Kašička, Václav
Enantiomeric helical forms of dicationic helquats, a novel family of charged helicene-like molecules, have been separated by capillary electrophoresis (CE) using sodium-phosphate buffer, pH 2.5, as background electrolyte and sulfated beta- and gamma-cyclodextrins as chiral selectors. Additionally, CE was used to determine barrier to helix inversion of helquats.
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