Unusual D:B-friedobaccharane and oxygenated friedelane-type triterpenoids from Salvadorean Celastraceae species

Three new triterpenoids, including two rare D:B-friedobaccharanes (leonatriol, 1 and leonatriolone, 2) and a 2,3-seco-2,24-epoxy-3,24-olide-D:A-friedooleanane (cassinolide, 3) were isolated from the root bark of Cassine xylocarpa and Celastrus vulcanicola, collected in El Salvador. Their stereostructures were elucidated on the basis of spectroscopic analyses, mainly 1D and 2D NMR techniques, spectrometric analyses, and comparison with data reported in the literature. The absolute configuration of 1 and 2 were determined by the application of the Riguera ester procedure and biogenetic considerations. The possible biogenetic pathway for cassinolide (3) is also discussed.