Asymmetric synthesis of the core cyclopentane of viridenomycin

The fully substituted cyclopentene ring with three stereogenic centers has been efficiently constructed for the first time using chiral bicyclic lactams, the insertion of the quaternary center being the key step; ring opening of chiral sulfates to the correct 1,2-dihydroxy substituents also played a major role in reaching 1 in suitable form (18) for further study.