1. Department of Lead Discovery, Boehringer Ingelheim Pharma GmbH & Co. KG, Birkendorfer Strasse 65, D-88397 Biberach, Germany, and Computer-Chemie-Centrum, Institute for Organic Chemistry, University of Erlangen-Nürnberg, Nägelsbachstrasse 25, D-91052 Erlangen, Germany