Vibsatins A and B, Two New Tetranorvibsane-Type Diterpenoids from <i>Viburnum tinus</i> cv. variegatus

Vibsatins A (<b>1</b>) and B (<b>2</b>), a pair of 14,15,16,17-tetranorvibsane-type diterpenoids that feature a bicyclo[4.2.1]­nonane moiety formed by a new C-13/C-2 bond, were isolated from the twigs and leaves of <i>Viburnum tinus</i> cv. variegatus. The structures and absolute configurations were elucidated by a combination of NMR spectra, optical rotation, and X-ray diffraction experiments. A possible biogenetic pathway is also proposed. Moreover, vibsatin A (<b>1</b>) enhanced the neurite outgrowth of NGF-mediated PC12 cells at a concentration of 10 μM