1. Department of Chemistry, University of York, Heslington, York YO1 5DD, United Kingdom, Geneva Biomedical Research Institute, Glaxo Wellcome Research and Development SA, 14, chemin des Aulx, 1228 Plan-les-Ouates, Geneva, Switzerland, and Glaxo Wellcome Medicines Research Centre, Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2NY, United Kingdom