REARRANGED NEOCLERODANE DITERPENOIDS FROM TEUCRIUM-BREVIFOLIUM AND THEIR BIOGENETIC PATHWAY

Seven new diterpenoids, teubrevins C-I (1-7 repectively), have been is olated from the aerial parts of Teucrium brevifolium and their structu res established by spectroscopic means, including an X-ray diffraction analysis of teubrevin I (7). All these diterpenoids belong to the neo -clerodane-type and five of them (3-7) possess an unusual rearranged s keleton having an eight-membered ring carbocycle. The conformation of this ring in each compound was established by exhaustive NMR spectrosc opic studies (3-6) and from X-ray data (7). A biogenetic pathway which explains the formation of the 5,10-seco-9(8-->19)abeo-neo-clerodane s keleton of 5-7 and their 7,8,17-trinor derivatives (3 and 4) starting from teubrevin D (2) is also discussed.