1. IPF PharmaCeuticals GmbH, Feodor-Lynen-Strasse 31, D-30625 Hannover, Germany, Institute for Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany, and Division of Experimental and Clinical Peptide Research, Hannover Medical School, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany