Stereospecific Sulfur-Mediated Cleavage of a Spirocyclobutanone: Synthesis of a Fully Functional Precursor to the CP Compounds

A reaction sequence made up of a Sakurai reaction, ketene cyclization, sulfur-directed Baeyer–Villiger reaction, and tandem lactone cleavage/isomerization provided the fully functionalized core of the CP compounds. Key steps were the methanolysis of 1 , which leads via 2 to the CP precursor 3 .