Preparation and Guest Binding of Novel β‐Cyclodextrin Dimers Linked with Various Sulfur‐Containing Linker Moieties.

Novel cyclodextrin dimers (1, 2, 3 and 4) whose cyclodextrins were linked with sulfur-containing linkers, namely a thiodipropanamide, a dithiodipropanamide, a thiodiethanamide, or a dithiodiethanamide linker, were synthesized by a reaction of 6-amino-6-deoxycycloheptaose 7 with the corresponding dicarboxylic acids. For their preparation, dicyclohexylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate were examined as coupling reagents. 1H NMR studies of the dimers suggested an intramolecular inclusion of the linker moiety to the cyclodextrin cavity, which affected the complexation of guest molecules. Dimer 4 was converted to another type of dimer 5 by reductive cleavage of the disulfide bond to generate thiol group-containing monomeric species followed by a substitution reaction with 6-O-tosyl derivative 6.