Three new dimeric diterpenes from Rhododendron molle

The first examples of dimeric diterpenoids from the Ericaceae family, birhodomolleins A-C (1-3), which dimerized from two grayanane diterpenes through a COC bond, were isolated from the flowers of Rhododendron molle. Their structures were elucidated by interpretation of their 1D and 2D NMR and other spectroscopic data.