Triphenylphosphine deoxygenation of beta-alkyl, beta,beta-dialkyl-, and beta,beta-spirocycloalkyl-substituted alpha-methylene-beta-peroxy lactones 3a-k, which are readily available by photooxygenation of the corresponding alpha,beta-unsaturated carboxylic acids 1, and cyclization of the resulting alpha-methylene-beta-hydroperoxy acids 2 constitute a convenient method for the preparation of a variety of alpha-methylene beta-lactones 5. Alternatively, the alpha-methylene-beta-hydroxy carboxylic acids 4 can be directly cyclized by benzenesulfonyl chloride in pyridine into these novel four-membered ring heterocycles 5.