Sesquiterpenes from Blumea balsamifera

Five new guaiane sesquiterpenes, blumeaenes E1 (1), E2 (2), K (3), L (4), and M (5), and one new eudesmane sesquiterpene, samboginone (6), along with three known compounds, cryptomeridiol, 3,3',5,7-tetrahydroxy-4'-methoxyflavanone, and austroinulin, were isolated from the leaves of the Philippine medicinal herb sambong, Blumea balsamifera. The absolute configuration of the new guaiane core was determined as 1S,7S,9S,10R by employing the modified Mosher's method. In the structure of 1, the absolute configuration of the epoxyangelic acid moiety was identified as 2S,3S using (R)-PGME as a chiral anisotropic auxiliary.