Synthesis of New Cantharimide Analogues Derived from 3-Sulfolene

New types of norcantharimide analogues were prepared by three methods: epoxidation, photooxidation, and bromination. Epoxidation of deoxynorcantharimide with m-chloroperoxybenzoic acid gave an isomeric mixture. The selective formation of the synisomers was attributed to dipole-dipole interactions between the peracid and imide moiety. Photooxidation of deoxynorcanthamide gave syn- and anti- hydroperoxide analogues through ene addition of singlet oxygen; the anti-hydroperoxide was the major product in this case, as a result of the steric effect of the imide ring. Bromination of deoxynorcantharimide and subsequent transformations gave a pyrrolidine and the phthalimide core structure.