Unexpected Stereochemistry in the Lithium Salt Catalyzed Ring Expansion of Nonracemic Oxaspiropentanes. Formal Syntheses of (−)-(4R,5R)-Muricatacin and the Pheromone (R)-Japonilure

The stereochemistry of the cyclobutanones 3, obtained by lithium salt catalyzed ring expansion of the optically pure oxaspiropentanes 2, depends not only on the lithium salt but also on the stereochemistry of 2. They constitute the starting material for the syntheses of the acetogenin (−)-(4R,5R)-muricatacin and the pheromone (R)-japonilure.