1. Department of Chemical Sciences, University of Camerino, Via S. Agostino 1, 62032 Camerino, Italy, Cancer Research Campaign Biomolecular Structure Unit and Cancer Research Campaign Cancer Therapeutics Centre, The Institute of Cancer Research, Cotswold Road, Sutton, Surrey SM2 5NG, U.K., Boehringer Mannheim Italia, Research Center, 20052 Monza, Italy, and Department of Pharmaceutical Technology and Biochemistry, Technical University of Gdansk, 80952 Gdansk, Poland