1. Medicinal Chemistry Division, Welsh School of Pharmacy, Cardiff University, King Edward VII Avenue, Cardiff CF10 3XF, UK; EPSRC X-ray Crystallography Service, Department of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK; and Rega Institute for Medical Research, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium