The study of enantioselectivity of all regioisomers of mono‐carboxymethyl‐β‐cyclodextrin used as chiral selectors in CE

Abstract

This work documents the influence of the position of single carboxymethyl group on the β-cyclodextrin skeleton on the enantioselectivity. These synthesized monosubstituted carboxymethyl cyclodextrin (CD) derivatives, native β-cyclodextrin, and commercially available carboxymethyl-β-cyclodextrin with degree of substitution approximately 3 were used as additives into the BGE consisting of phosphate buffer at 20 mmol/L concentration, pH 2.5, and several biologically significant low-molecular-mass chiral compounds were enantioseparated by CE. The results indicate that different substituent location on β-cyclodextrin skeleton has a significant influence on the enantioseparation of the investigated enantiomers. The enantioselectivity of 2(I)-O-regioisomer was better than with native β-cyclodextrin. Comparable results to native β-cyclodextrin were obtained for 6(I)-O- regioisomer and the enantioselectivity of 3(I)-O-regioisomer was even worse than with native β-cyclodextrin. Commercially available derivative of CD provides better resolutions than the monosubstituted carboxymethyl CD derivatives for most of the investigated analytes.

Influence of substituent position and cavity size of the regioisomers of monocarboxymethyl‐α‐, β‐, and γ‐cyclodextrins on the apparent stability constants of their complexes with both enantiomers of Tröger's base

“…In the present work, all the CE separations were carried out with 20 mmol/L sodium phosphate buffer, pH 2.5, as the BGE. This electrolyte was chosen because of our positive experience as we reached successful enanatioseparations of TB using all the monosubstituted CDs previously . TB is positively charged at such pH (p K a 4.75) and degree of dissociation of the monosubstituted carboxymethyl‐CDs (p K a 3.6) is very limited .…”

“…Beside the studies on persubstituted CD derivatives there are also papers focused on the enantioselectivity of monosubstituted CDs. In such case three isomers may exist substituted at the position C2, C3, or C6, respectively . The results revealed that both the position of carboxymethyl group within the CD skeleton and the size of the CD cavity strongly influenced the enantioseparation ability of these selectors toward the studied analytes.…”

Monosubstituted Cyclodextrins as Precursors for Further Use

“…Org. [78,82,83,85,[108][109][110] Per-O-methyl-2 A -O-carboxymethyl--CD was prepared from per-O-methyl-2 A -O-allyl--CD by oxidation with NaIO 4 /RuCl 3 [83] or from per-O-methyl-2 A -O-formylmethyl--CD with NaClO 2 /NaH 2 PO 4 [111] and also by treatment of permethylated 2 A -O-hydroxy--CD with iodoacetate. 2016, 5322-5334 www.eurjoc.org achieved with LiH in DMSO together with a catalytic amount of LiI.…”

“…[78,82,83,85,[108][109][110] 3 A -O-Formylmethyl--CD was synthesised from 3 A -O-cinnamyl--CD by reductive ozonolysis (O 3 /Me 2 S). [78,82,83,85,[108][109][110] 3 A -O-Formylmethyl--CD was synthesised from 3 A -O-cinnamyl--CD by reductive ozonolysis (O 3 /Me 2 S).…”

“…[55,82,85] The yields are usually above 10 % and no other monosubstituted derivatives are formed, which facilitates the separation process. [78,82,83,85,[108][109][110]112] 6 A -O-Formylmethyl CD derivatives were prepared only as peracetates. 6 A -O-Carboxymethyl-α-, --or -γ-CDs and their peracetylated or permethylated derivatives were prepared in a similar way as the 2 A -and 3 A -O derivatives (see above).…”