1. Department of Pharmaceutical Chemistry, University of Pavia, Via Taramelli 12, I-27100 Pavia, Italy, Merck KGaA, LSP R&D MDA, Frankfurter Str 250, 64271 Darmstadt, Germany, Centro Grandi Strumenti, University of Pavia, Via Bassi I-27100 Pavia, Italy, and Department of Biochemistry, University of Pavia, Via Taramelli 3, I-27100 Pavia, Italy