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

<UFIGR ID="ol035061rn00001">The stereochemistry of the cyclobutanones <BO>3</BO>, obtained by lithium salt catalyzed ring expansion of the optically pure oxaspiropentanes <BO>2</BO>, depends not only on the lithium salt but also on the stereochemistry of <BO>2</BO>. They constitute the starting material for the syntheses of the acetogenin (−)-(4R,5R)-muricatacin and the pheromone (R)-japonilure.