A cyclic acetal tethered intramolecular Diels-Alder cycloaddition: studies directed toward a total synthesis of (±)-fusidilactone C

Cycloaddition precursor (I) allows a facile and unique intramolecular Diels—Alder cycloaddition, proceeding highly endo-selective to provide the endo-I and endo-II products (II) and (III).