Formation of unexpected substitution patterns in sulfonylbutylation of cyclomaltoheptaose promoted by host–guest interaction Original Research Article

The distribution of substituents in sulfonylbutylethers of cyclomaltoheptaose (β-cyclodextrin) formed in aqueous medium has been determined by gas chromatography after hydrolysis and formation of the permethylated sulfonylfluoride derivatives. In contrast to other etherification reactions of β-cyclodextrin, preferred substitution in position 3 of the glucose units has been detected. From 1H NMR and microcalorimetric experiments, the formation of host–guest complexes by β-cyclodextrin and the reagent 1,4-butane sultone in water became evident. This spatial preorganization presumably favors the reaction with the O-3. In contrast, in methyl sulfoxide preferred 2-O-alkylation was obtained, indicating that host–guest interaction does not influence regioselectivity in this solvent.