Influence of intramolecular hydrogen bonds on the binding potential of methylated β-cyclodextrin derivatives

Abstract

SummaryVarious heptasubstituted derivatives of β-cyclodextrin (β-CD) bearing 1, 2 and 3 methyl substituents per glucose unit were synthesized by regioselective methods. Binding free energies and binding enthalpies of these hosts towards 4-tert-butylbenzoate and adamantane-1-carboxylate were determined by isothermal titration microcalorimetry (ITC). It was found that methyl substituents at the secondary positions of β-CD lead to a tremendous reduction of the binding potential, while methylation at the primary positions significantly improved binding. Stabilizing intramolecular hydrogen bonds between the glucose units were made responsible for the high binding potentials of those β-CD derivatives that possess secondary hydroxy groups.

Methyl-Beta-Cyclodextrins: The Role of Number and Types of Substituents in Solubilizing Power

“…Our findings are in agreement with those of Wenz, who found that the monomethyl substitution at position C‐6 is the most preferred, followed by dimethyl substitution at positions C‐2 and C‐6 (corresponding to DIMEB). His conclusion was that methylation at the primary position (C‐6) significantly improved binding, whereas methylation at the secondary position (C‐2, C‐3) reduced it.…”

Layer‐by‐layer coating of textile with two oppositely charged cyclodextrin polyelectrolytes for extended drug delivery

“…The negative values of standard formation enthalpies indicated that the formation of complexes between TBBA and βCD or polymer was a weak exothermic process. Binding constant K f of TBBA with βCD was found 17.3 k M −1 in good agreement with the literature . In the event of polyEPG‐CD‐10, polyEPG‐CD‐1, polyEP‐CD and polyCTR‐CD complexed with TBBA, the association constant was successively appeared 26.6, 11.1, 8.9, and 2.6 k M −1 .The binding constant of TBBA was outstandingly enhanced with the oppositely charged host (polyEPG‐CD) and was significantly decreased with the identically charged host (polyCTR‐CD) because the charge could provide the supplementary contribution of binding interaction .…”

“…Binding constant K f of TBBA with bCD was found 17.3 kM 21 in good agreement with the literature. 65,66 In the event of polyEPG-CD-10, polyEPG-CD-1, polyEP-CD and polyCTR-CD complexed with TBBA, the association constant was successively appeared 26.6, 11.1, 8.9, and 2.6 kM 21 .The binding constant of TBBA was outstandingly enhanced with the oppositely charged host (polyEPG-CD) and was significantly decreased with the identically charged host (polyCTR-CD) because the charge could provide the supplementary contribution of binding interaction. [67][68][69][70][71] The K f value in polymers (polyEPG-CD-10) was higher than pristine CD which was rarely observed.…”

Space filling of β-cyclodextrin and β-cyclodextrin derivatives by volatile hydrophobic guests

“…This destabilization leads to a reduction of the binding potential, because of an unfavorable negative binding entropy. Recently, we also found a diminished binding potential for those β-CD derivatives methylated at the 2- and 3-positions [38]. …”