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Evaluation of norbornene‐ β‐cyclodextrin‐based monomers and oligomers as chiral selectors by means of nonaqueous capillary electrophoresis
Author(s) -
Eder Karoline,
Sinner Frank,
Mupa Mathew,
Huber Christian G.,
Buchmeiser Michael R.
Publication year - 2001
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/1522-2683(200101)22:1<109::aid-elps109>3.0.co;2-p
Subject(s) - norbornene , chemistry , monomer , ether , capillary electrophoresis , polymer chemistry , chromatography , organic chemistry , polymer
Norbornen‐5‐yl carboxylic acid and norbornen‐5‐ylmethylsilyl ether‐based β‐cyclodextrins (β‐CDs) containing up to three norbornene ester and up to five norbornene silyl ether units have been prepared from β‐CD and norbornen‐5‐carboxylic chloride and norbornen‐5‐ylmethyldichlorosilane, respectively. Oligomers ( n = 2—4) were prepared therefrom using ring‐opening metathesis polymerization (ROMP). Monomeric and oligomeric substituted β‐CDs were evaluated as chiral selectors in nonaqueous capillary zone electrophoresis using 35 m M sodium bicarbonate in N ‐methylformamide (NMF) as background electrolyte. Both monomeric and oligomeric norbornene ester‐ and norbornene silyl ether‐type selectors showed good enantioresolution for dansylated (DNS‐) amino acids using concentrations of the chiral selector of up to 4% w/v. A significant improvement in resolution was observed upon the introduction of up to five norbornene silyl ether units into a β‐CD molecule, whereas higher degrees of substitution with norbornen‐5‐yl‐carboxyl groups lead to a reduction in enantioresolution of DNS‐amino acids. Thus, pentakis(norbornen‐5‐ylmethylhydroxysiloxyl)‐β‐CD turned out to be superior to mono(norbornen‐5‐ylmethylhydroxysiloxyl)‐β‐CD in terms of enantioresolution. Moreover, norbornene silyl ether‐type selectors were found to be more efficient than norbornene ester‐type selectors. Finally, oligomeric selectors were found to possess superior or at least comparable enantioselectivity in the separation of DNS‐amino acids compared to the parent monomers. A maximum in enantioresolution was obtained with oligo(pentakis(norbornen‐5‐ylmethylhydroxysiloxyl)β‐CD).