Semi-syntheses of new stemofoline derivatives

Semi-syntheses of several new stemofoline derivatives are described. Acidic hydrolysis of the tetronate moiety of stemofoline, followed by re-esterification gave homologues of stemofoline and isostemofoline. Hydrazinolysis resulted in new pyridazinones. Oxidative cleavage of stemofoline afforded the pentacyclic cage lactone, recently prepared by total synthesis.