Formation of unexpected substitution patterns in sulfonylbutylation of cyclomaltoheptaose promoted by host-guest interaction

The distribution of substituents in sulfonylbutylethers of cyclomaltoheptao se (beta-cyclodextrin) formed in aqueous medium has been determined by gas chromatography after hydrolysis and formation of the permethylated sulfonyl fluoride derivatives. In contrast to other etherifrcation reactions of beta -cyclodextrin, preferred substitution in position 3 of the glucose units ha s been detected. From H-1 NMR and microcalorimetric experiments, the format ion of host-guest complexes by beta-cyclodextrin and the reagent 1,4-butane sultone in water became evident. This spatial preorganization presumably f avors the reaction with the O-3. In contrast, in methyl sulfoxide preferred 2-O-alkylation was obtained, indicating that host-guest interaction does n ot influence regioselectivity in this solvent. (C) 2000 Elsevier Science Lt d. All rights reserved.