A BASE-CATALYZED H/D EXCHANGE-REACTION IN THE 6-(1-PYRIDINIO)-6-DEOXY DERIVATIVES OF CYCLODEXTRINS

Mono[6-(1-pyridinio)-6-deoxy]-a-cyclodextrin and its analogs exchanged the a-hydrogens of their pyridinio moieties with the deuteriums of solvent D2O in an alkaline buffer solution via the formation of the pyridinium ylide intermediates. The H/D exchange reaction was facilitated by the hydrophobic cavity of cyclodextrin, as well as by a substitution of the additional pyridinio group for the primary OH group, especially in the adjacent glucopyranose moiety of the cyclodextrin residue. On the other hand, the reaction was moderately retarded by an increase in the ionic strength of the solution, and markedly retarded by inorganic anions, such as I-, SCN-, and ClO4-, which were strongly bound to the cavity of cyclodextrin.