1. Institute of Molecular Chemistry, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, Institute of Organic Chemistry, University of Vienna, Währinger Strasse 38, 1090 Vienna, Austria, Institute of Mineralogy, Crystallography and Structural Chemistry, Technical University of Vienna, Getreidemarkt 9, 1040 Vienna, Austria, and Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands