Reaction of cyclic ketals with ceric ammonium nitrate in acetonitrile/water

The possibility of performing the hydrolysis of cyclic acetals and ketals under basic or mildly alkaline conditions by ceric ammonium nitrate (CAN) in MeCN/H2O or in 10% aq. methanol is rejected. However a role for Ce(IV) as Lewis acid is evidenced at pH 4.4. Under these conditions, which allow hydrolysis of cyclic ketals leaving glycosidic bonds unaltered, a selectivity of ketal cleavage due to steric hindrance is also observed. Similar yields are obtained when acetone/water replaces MeCN/H2O as solvent.