List, Anja;Zeiler, Evelyn;Gallastegui, Nerea;Rusch, Marion;Hedberg, Christian;Sieber, Stephan A.;Groll, Michael Omuralide and Vibralactone: Differences in the Proteasome- β-Lactone-γ-Lactam Binding Scaffold Alter Target Preferences Angew. Chem. Int. Ed. 2013 53 571-574