Structures of furanovibsanins A–G from Viburnum awabuki

The structures of nine new 7-membered vibsane-type diterpenes named furanovibsanin A (), 3-O-methylfuranovibsanin A (), furanovibsanin F (), furanovibsanin B (), 7-epi-furanovibsanin B (), furanovibsanin C (), furanovibsanin D (), furanovibsanin E (), and furanovibsanin G (), isolated from the leaves of Viburnum awabuki, were elucidated by intensive analyses of 2D NMR data and comparison of NMR data of the previously known vibsanins C and E. Their structures feature in a furan or a cyclic enol acetal ring forming on the C-4 and C-5 positions in vibsanin C ().