Synthesis and NMR characterization of β‐alanine‐bridged hemispherodextrin, a very efficient chiral selector in EKC

Abstract

A capped derivative of beta-CD (THALAH) was synthesized and characterized by NMR spectroscopy at different pH values. A trehalose moiety, bonded through beta-alanine bridges to the CD cavity, is included in the capping unit, giving peculiar properties to this molecule. The hemispherodextrin thus obtained was tested as a chiral selector in EKC. At neutral pH, the monocationic species of THALAH behaves as a very efficient selector separating successfully all the 11 tested enantiomeric pairs of dansyl-derivatives of amino acids, some of them even at concentrations as low as 0.15 mM. The differences observed in the migration order among the different systems give suggestions about the mechanism of molecular recognition between the selector and the analytes.

Cyclodextrins in capillary electrophoresis enantioseparations – Recent developments and applications

“…4) has been synthesized and evaluated by Cucinotta et al [64]. The new selector proved to be very effective for the enantioseparation of DNS-amino acids yielding baseline separations at CD concentrations as low as 0.25 mM in ammonium acetate buffer, pH 6.8, as shown for DNSSer in Fig.…”

Recent progress in capillary electrophoretic analysis of amino acid enantiomers

“…On the other hand, various types of cationic CDs have been synthesized and applied to the CDEKC analysis of amino acid racemates [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62]. In contrast to anionic CDs, BGSs with pH 5-8,which is effective for separating neutral amino acids, are applied to EKC using cationic CDs (Table 2).…”

“…When the charged CDs interact with racemic amino acids, the analytes migrate at a different velocity from a surrounding aqueous phase due to the electrophoretic migration of the ionic CDs. Although various anionic [34][35][36][37][38][39][40][41][42][43] and cationic CDs [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] are synthesized for CDEKC as summarized in Table 2, sulfated CDs (S-CDs) [34,35] and highly sulfated CDs (HS-CDs) [36][37][38][39][40][41] are still the predominant CSs due to their resolution powers and commercial-availability. Since commercially available S-CDs and HS-CDs from Beckmann Coulter are not single isomers but a mixture of sulfated CDs with a different degree of substitution (average; 9 and 12, respectively), a wide range of OTG, 1-S-octyl-␤-d-thioglucopyranoside; DTDP, 3-(4,6-dichloro-1,3,5-triazinylamino)-7-dimethyamino-2-methylphenazine; LED-IF, light-emitting diode-induced fluorescence.…”

Modified cyclodextrins for fast and sensitive chiral‐capillary electrophoresis‐mass spectrometry

“…This electrostatic interaction increases the selector-analyte complex formation, changing the electrophoretic mobility of analyte (occasionally, even its sign) and increasing the resolution of the chiral separation. This strong interaction permits to drastically lower the concentration of the selector necessary to obtain a satisfying resolution between the enantiomers [38][39][40][41][42][43].…”