an intra- or intermolecular [2+2]-photocycloaddition reaction. Typical reaction conditions are irradiation at λ = 254 nm in diethyl ether or an alcohol as the solvent. The bi-, tri- or tetracyclic products so obtained can be further utilized by ring opening either of the lactone or the cyclobutane ring. Lactone ring opening led to the use of a tetramide photocycloaddition product as a conformationally