The novel melampolides (11R)-11,13-dihydro-schkuhriolide (7), (11S)-11,13-dihydro-schkuhriolide (8), and schkuhrioidiol (11), along with the known constituents, frutescin (1), schkuhriolide (2), frutescinic acid (4), allo-schkuhriolide (5), and epoxyschkuhriolide (6) were isolated from the aerial parts of Schkuhria schkuhrioides. The structures of the new compounds were determined by spectroscopic methods. Compounds 1, 2, 4, 5, and 6 displayed no significant cytotoxic or antimicrobial activities.

Eight new eremophilanolides (1, 2, 4-7, 9, and 10), a new eremophilane (13), and several known compounds were isolated from the roots and aerial parts of Senecio mairetianus. The chemical structures were proposed taking into consideration spectroscopic analyses and chemical transformations. X-ray diffraction analysis of 2, 4, and 9 confirmed their structures. The stereochemistry of 1,10-epoxy-8alpha-methoxyermophilanolide (3) was determined. Compounds 4-7, 9, and 10 are possible artifacts obtained by preparation of the alkaloidal extract.

No abstract

The acid catalysed transformation of the melampolide schkuhriolide 1 provided a mixture of epimers and the oplopanolide 5 via sequential rearrangements.

Treatment of budlein B with acid gave a H-4b,H-9a-oplopane via lactone cleavage, allylic rearrangement, transannular cyclization and pinacol-type rearrangement. This transformation is stereochemically complementary to that of schkuhriolide, which produces a H-4a,H-9b-oplopane.