Two methods (A: ring opening to acylketenes followed by intramolecular ketene trapping and B: methoxide-mediated ring opening followed by cyclization of the hydroxy esters thus formed) have become available for the synthesis of lactones and/or cyclic ethers from 1, 3- dioxin-4-ones having 1-∼ 4-hydroxyalkyl group at the 6-position. Mechanism and scope of both methods have been clarified.