Modified Calix[4]crowns as Molecular Receptors for Barium

Invited for this month's cover picture is the group around Dr. Constantin Mamat at the Institute of Radiopharmaceutical Cancer Research at the Helmholtz‐Zentrum Dresden‐Rossendorf (Germany) together with Prof. Martin Köckerling from the University of Rostock (Germany). The cover picture shows the ability of special functionalized calix[4]crown‐6 derivatives to stably bind group 2 metals like barium. This binding mode is highly important for radiopharmaceutical applications not to lose the respective radiometal in vivo to avoid high background signals and/or false positive results and damages in other tissues. For this purpose, different calix[4]crowns were tested, based upon their potential to stably bind barium as surrogate for radium. Radium nuclides are known to be good candidates for usage in α‐targeted therapies. Currently, radium‐223 is used for α‐therapy of bone metastases because of its calcium mimetics. Our aim is to apply the radium to treat other cancer tissues. That's why we need novel chelators to stably fix groups 2 metals like barium and radium. Read the full text of their Full Paper at https://doi.org/10.1002/open.201800019.