The relative rates of acid-catalyzed rearrangements of epoxy esters to [3.2. 1] bicyclic orthoesters, the subsequent rearrangements of these ortho esters to substituted tetrahydrofurans, and the rates of orthoester hydrolysis at pH 4.75 were measured in NMR kinetics experiments. The ease of formation and stabilities of these orthoesters compared favorably with the OBO-type [2.2. 2] bicyclic orthoesters typically used as protecting groups ...