Triphenylphosphine deoxygenation of &alkyl, B, B-dialkyl-, and@,@-spirocycloalkyl- substituted a-methylene-@-peroxy lactones 3a-k, which are readily available by photooxygenation of the corresponding a,@-unsaturated carboxylic acids 1, and cyclization of the resulting a-methylene-b-hydroperoxy acids 2 constitute a convenient method for the preparation of a variety of a-methylene &lactones 5. Alternatively, the a-methylene-8- ...