Preparation and guest binding of novel beta-cyclodextrin dimers linked with various sulfur-containing linker moieties

Novel cyclodextrin dimers (1, 2, 3 and 4) whose cyclodextrins were linked w ith sulfur-containing linkers, namely a thiodipropanamide, a dithiodipropan amide, a thiodiethanamide, or a dithiodiethanamide linker, were synthesized by a reaction of 6-amino-6-deoxycycloheptaose 7 with the corresponding dic arboxylic acids. For their preparation, dicyclohexylcarbodiimide, 1-(3-dime thylaminopropyl)-3-ethylcarbodiimide and (benzotriazol-1-yloxy)tripyrrolidi nophosphonium hexafluorophosphate were examined as coupling reagents. H-1 N MR studies of the dimers suggested an intramolecular inclusion of the linke r moiety to the cyclodextrin cavity, which affected the complexation of gue st molecules. Dimer 4 was converted to another type of dimer 5 by reductive cleavage of the disulfide bond to generate thiol group-containing monomeri c species followed by a substitution reaction with 6-O-tosyl derivative 6.