New guaipyridine sesquiterpene alkaloids from Artemisia rupestris L.

Three new guaipyridine sesquiterpene alkaloids, rupestine A, B, C (1-3, resp.), and the new nor-sesquiterpne alkaloid rupestine D (4) were obtained from the flowers of Artemisia rupestris L. Their structure,, were elucidated on the basis of sepectroscopic data and by comparison with those of the related compounds reported in the literature. In addition, the absolute configurations of 2 and 4 were determined by single-crystal X-ray diffraction analyses.