The periodate oxidation of 4,4,6,6-tetramethylcyclohexane-1,2,3-triol in neutral or acidic aqueous solution did not give the expected 2,2,4,4-tetramethylpentane-1,5-dial, but exo-7-hydroxy-2,2,4,4-tetramethyl-6,8-dioxabicyclo[3,2,1]octane, produced by a partial oxidation to the hydroxy-dialdehyde, followed by closure of two intramolecular acetal linkages to give the observed product.