Abstract: A general, highly stereoselective approach to the synthesis of spiroketal systems of the 1, 7-dioxaspiro [5.51 undecane and l, ddioxaspiro [4S] decane families is discussed. The key reaction in the approach features oxidation of a suitably substituted furfurol derivative 1 to afford pyranone 2, which subsequently undergoes stereoselective intramolecular ketalization under acidic conditions to furnish spiroketal 3, carrying the 2, 6-anti ...