We describe the first synthesis of spiroepoxy-β-lactones obtained via epoxidation of ketene dimers. These compounds display unexpected stability that may be due to a double anomeric effect garnered from analysis of bond lengths by X-ray crystallography of one spirocycle in comparison to calculated bond lengths of related structures. These new strained intermediates display interesting reactivity leading to a butenolide, an α-hydroxyketone, a triol, an α-chloroketone, and an α-azidoketone.