Four New Carvotanacetone Derivatives from Sphaeranthus ukambensis, Inhibitors of the Ubiquitin-Proteasome Pathway - Pouny, Isabelle; Vispé, Stéphane; Marcourt, Laurence; Long, Christophe; Vandenberghe, Isabelle; Aussagues, Yannick; Raux, Roselyne; Chalo Mutiso, Patrick B.; Massiot, Georges; Sautel, François (Planta Medica, 2011)