Manganese (II1) oxidation of malonic acid in the presence of alkenes results in the formation of spiro-fused lactones, 2, 7-dioxaspiro [4.4] nonane-1, 6-diones. Terminal alkenes produce a mixture of the three possible diastereomers. The stereochemistry of the diastereomeric spirodilactones was determined by NMR and corroborated by the intensity of the coupled IR carbonyl stretching frequencies. 1, 1, 6, 6-Tetrasubstituted 1, 5-hexadienes give in one ...