1. Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
2. School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, United Kingdom
3. Ben May Institute for Cancer Research, University of Chicago, Chicago, Illinois 60637
4. NewChem Technologies Ltd., Bedson Building, Kings Road, Newcastle upon Tyne NE1 7RU, United Kingdom