Three novel epoxy-clerodanes bearing a furan ring from Croton hypoleucus

Three new epoxy-clerodanes bearing a furan ring hypoleins A?C, were isolated from the aerial parts of Croton hypoleucus, along with the known compounds crotonpenes A and B. The structure of all compounds was elucidated on the basis of extensive ID and 2D NMR and mass (HR-ESIMS) spectroscopic data analyses. All of them possess an epoxy ring at C-3/C-4, and one furan ring at C-12. The absolute configuration of hypolein A was established by X-ray diffraction analysis. The crystal packing of hypolein A showed two types of intermolecular contacts such as CH?O and CH?? (Furan ring) interactions.