C-15-functionalized eudesmanolides from Mikania campanulata.

The aerial parts of Mikania campanulata Gardner afforded the nine new eudesmanolides (1S,4S,5S,6S,7S,10R)-1-hydroxy-15-acetoxyeudesm-11(13)-en-6,12-olide (1), (1S,4S,5S,6S,7S,10R)-1,4-dihydroxy-15-acetoxyeudesm-11(13)-en-6,12-olide (2), (1R,4S,5S,6S,7S,10R)-1,4-dihydroxy-15-acetoxyeudesm-11(13)-en-6,12-olide (3), (1R,4S,5S,6S,7S,10R)-1-hydroxy-4,15-diacetoxyeudesm-11(13)-en-6,12-olide (4), (1S,4R,5S,6S,7S,10R)-1,15-diacetoxy-4-hydroxyeudesm-11(13)-en-6,12-olide (5), (1S,5S,6S,7S,10R)-1-hydroxy-15-acetoxyeudesma-4(15),11(13)-dien-6,12-olide (6), (1S,5S,6S,7S,10R)-1,15-dihydroxyeudesma-3,11(13)-dien-6,12-olide (7a), (1S,2R,5S,6S,7S,10R)-1,2,15-trihydroxyeudesma-3,11(13)-dien-6,12-olide (8a), and (1R,6S,7S,10R)-1,15-dihydroxyeudesma-4,11(13)-dien-6,12-olide (9a), among which the last three were characterized as their corresponding peracetates (7b-9b). The structures of 1-6 and 7b-9b were elucidated using 1D and 2D NMR measurements, while that of major constituent 1 was confirmed by single-crystal X-ray diffraction analysis, and its absolute configuration evidenced from vibrational circular dichroism measurements, which were compared to results obtained from density functional theory calculations. The chemistry of the large genus Mikania is briefly analyzed.

Sesquiterpene lactones from Centaurea tweediei.

Aerial parts of Centaurea tweediei from Argentina afforded as the main constituent the sesquiterpene lactone onopordopicrin and minor amounts of a new heliangolide, a new guaianolide, a new eudesmanolide, a new eudesmane acid and the lignans arctigenin and matairesinol.

A glycosidic eudesmanolide from Hyaloseris salicifolia.

The flowers of Hyaloseris salicifolia afforded known ivasperin, while the leaves afforded ivasperin and 2-O-(6'-O-acetyl-beta-D-glucopyranosyl)-ivasperin, whose structure was determined by spectroscopic methods.