A Hydrophilic Cyclodextrin Duplex Forming Supramolecular Assemblies by Physical Cross‐Linking of a Biopolymer

Abstract

New beta-cyclodextrin (beta-CD) dimeric species have been synthesised in which the two CD moieties are connected by one or two hydrophilic oligo(ethylene oxide) spacers. Their complexation with sodium adamantylacetate (free adamantane) and adamantane-grafted chitosan (AD-chitosan) was then studied by different complementary techniques and compared with their hydrophobic counterparts that contain an octamethylene spacer. Isothermal titration calorimetry experiments have demonstrated that the use of hydrophilic spacers between the two CDs instead of aliphatic chains makes almost all of the CD cavities available for the inclusion of free adamantane. Investigation of the interaction of the CDs with AD-chitosan by viscosity measurements strongly suggests that the molecular conformation of the CD dimeric species plays a crucial role in their cross-linking with the biopolymer. The derivative doubly linked with hydrophilic arms, also called a duplex, has been shown to be a more efficient cross-linking agent than its singly bridged counterpart, referred to as a dimer. Hence, only 0.5 molar equivalents of the hydrophilic duplex with respect to adamantane was required to obtain the maximum viscosity, whereas in the case of the duplex with aliphatic spacers, the maximum viscosity was achieved with a [duplex]/[AD] ratio of about 1.7 (corresponding to a [CD]/[AD] ratio of 2.5), but with a higher value. To clarify the relationships between the molecular architecture and complexation properties, computational studies were also performed that clearly confirmed the importance of double bridging.

Regiospecific Tandem Azide‐Reduction/Deprotection To Afford Versatile Amino Alcohol‐Functionalized α‐ and β‐Cyclodextrins

“…This Angewandte Chemie selectivity cannot be detected in the double debenzylation reaction of CD 2 to give diol 4, because 2 can be regarded as either a 6 A -6 E or a 6 A -6 D diol, which results in the equivalence of the two hydroxy groups. Indeed, when b-CD-diol 4 was monoalkylated in a previous study, [19] we obtained, as expected, an inseparable 1:1 mixture of 6 A -hydroxy-6 E -alkyl 17 and 6 A -hydroxy-6 D -alkyl 18, resulting from the statistical alkylation of the two undistinguishable alcohols (Scheme 5). Therefore, this pathway is ineffective for the formation of a single b-CD compound, [20] whereas the regiospecific tandem reaction clearly reveals all its interest, particularly if we aim to use those compounds for asymmetric induction.…”

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2007–2008

“…Complexes with busulfan antercancer agent (Menuel, et al, 2007) Bis-β -cyclodextrin linked with ethylene oxide TOF (DHB), ESI Complexes with adamantane (Bistri, et al, 2007) Bis-β-cyclodextrin linked with stilbene TOF (DHB) For construction of supramolecular structures (Kuad, et al, 2007) β-Cyclodextrin dimers TOF/TOF (DHB) Synthesis by click chemistry (Mourer, et al, 2008) β-CD fatty acid esters MALDI Chain lengths (C4---C14) synthesised by trans-esterification of β-CD by vinyl fatty ester using thermolysin in DMSO (Choisnard, et al, 2007) β-CD linked to azobenzene via PEG linker TOF (DHB) For studies on thermal and photochemical conformation switching ) β-CD linked to Ru(II)-terpyridine TOF Encapsulation by CD. Article in Korean β-CD monoesterified with 3-Forms large aggregates w TOF ith two Glycolipids ((E)-dec-2-enyl)-dihydrofuran-2,5-dione recognition sites Gives blue or green fluorescence depending on solvent (Huo, et al, 2008) CDs with guanidinoalkylamino and aminoalkylamino groups on their primary side Synthesis, characterization and properties TOF (DHB) (Mourtzis, et al, 2008) 5-N-β -Cyclodextrincarboxamide-5-methyl-1-pyrroline N-oxide MALDI Improved spin trapping.…”

Modified Cyclodextrins with Pendant Cationic and Anionic Moieties as Hosts for Highly Stable Inclusion Complexes and Molecular Recognition

“…They have been shown to increase binding affinities significantly, yet the flexibility of a single bridge often causes that the cyclodextrin macrocycles act independently forming a complex with 2:1 stoichiometry with no enhancement in binding [17]. In contrast, cyclodextrin duplexes connected with more than one linking group are much more difficult to prepare; in fact, up until today only a few well-defined doubly [18][19][20][21][22][23] and triply [24] bridged duplexes have been reported. Two of these hosts [18,23] hold a record among cyclodextrin binary complexes with neutral organic guest molecules reaching values of K a up to 10 10 M -1 .…”