Two new diterpenoids, teubrevins A and B, have been isolated from the aerial parts of Teucrium brevifolium (Jabiie). The structures of teubrevin A [(1R,12S)-3~acetoxy&,18;15,16-diepoxy-6~-hydroxy-10-oxo-5,10-seco-1,6~yclo-neo-cleroda-5( 19).13(16),14-t&n-20,12-elide., 11 and its Ifi-hydroxy derivative (teubrevin B, 2) were established by spectroscopic means, including an X-my diffraction analysis of the former. Compounds 1 and 2 possess a new 5.10~sezo-1,6-cycl~~o-clerodane skeleton, the biogenesis of which is briefly discussed. The genus Teucrium (family Labiatae) is so far the most abundant natural source of neo-clemdane and 19nor-neo-clerodane diterpenoidsl. These compounds have attracted a great interest on account of their useful antifeedant activity2 and fascinating and challenging stmctures~. In our continued search for new insect antifeedants from natural source&3. we have studied Teucrium brevijofium Schreber, a species which grows in small areas of Greece. We wish to report herein the isolation and structure determination of two new rearranged neo-clerodane diterpenoids, teubrevins A (1) and B (2), possessing a 5,10-scco-1,6-cycle-neo-clerodane skeleton which, to the best of our knowledge, has now been found for the first time in natural products.
RESULTS AND DISCUSSION
Repeated chromatography of the acetone extract of the aerial parts of T. brevifolium (see Experimental) led to the isolation of compounds 1 and 2 (teubrevins A and B, respectively).
Combustion analysis and low-resolution mass spectrometry iIIdiCated the IIIOkCUhI formula C22H2408
for teubrevin A (1) and its IR spectrum showed hydroxyl (3440 cm-l), furan (3140, 1600, 1505. 875 cm-l), acetate (1715, 1260 cm-l), y-lactone (1760 cm-l), ketone (1705 cm-l) and exocyclic methylene (3090, 1650,