Recognition of Ionic Guests by Ionic β‐Cyclodextrin Derivatives

Abstract

Inclusion compounds of cationic, anionic, and neutral p-substituted derivatives of tert-butylbenzene complexed in beta-cyclodextrin and its ionic 6-mono and 6-hepta derivatives were systematically investigated by isothermal titration calorimetry (ITC). All inclusion compounds showed 1:1 stoichiometry with binding constants ranging from 10 to 3 x 10(6) M(-1). The binding free energies could be subdivided into apolar and electrostatic contributions. The electrostatic interactions could be quantitatively described by Coulomb's law by taking into account the degree of protonation of hosts and guests, the orientations of the guests within the hosts, and ion shielding as described by the Debye-Hückel-Onsager theory. The orientations of the guests within the cyclodextrin cavities were determined by ROESY NMR spectroscopy.

Access to Versatile β‐Cyclodextrin Scaffolds through Guest‐Mediated Monoacylation

“…Introduction of at hiol group to CD 1 was desired due to the compatibility of thiols with aqueous ligationc hemistry and applications in bioconjugation. [55][56][57] Guests 2 and 3 contain alkyl linkers of differing length which will affect the rate of reaction with CD 1 and the propensity to form an intramolecular self-inclusion complex following monoderivatization. [45] The guests were activated as esters of salicylic acid to increaset he guests'a queous solubility and to provide favorable electrostatic interactions between the activated ester and the primary amines of 1.…”

Cellular delivery of polynucleotides by cationic cyclodextrin polyrotaxanes

“…The resulting CD derivatives, such as hydroxypropyl-CD, often show higher solubility in water and lower toxicity than the corresponding native CDs [20]. Amino functionalities have been multivalently attached to CDs via thioether linkages at the primary positions leading to highly water-soluble CD derivatives, which show improved binding affinities and aqueous solubilities compared to native CDs [21][22][23]. CDs can complex not only monomeric guests but also polymeric ones.…”

Advanced CE for chiral analysis of drugs, metabolites, and biomarkers in biological samples

“…The improved chiral recognition was observed many times with charged CDs compared with neutral ones as a result of enhanced stability of host-guest complexes due to additional electrostatic (Coulomb) interactions of oppositely charged functional groups of complexing partners as it was demonstrated by CE [110,119] as well as NMR measurements [120]. Here, the complex stability depends on charge that is important especially for the effective use of ionizable CD derivatives in CE (having carboxyl or amino groups in macrocycle), see Section 2.2.1.…”