1. School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, Norfolk NR4 7TJ, U.K.
2. Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, U.K.
3. GlaxoSmithKline, Gunnels Wood Road, Stevenage, Hertfordshire SG1 2NY, U.K.
4. School of Chemistry, University of St. Andrews, Fife KY16 9ST, U.K.
5. Department of Chemistry & Forensics, Nottingham Trent University, Clifton, Nottinghamshire SG5 5BG, U.K.
6. Département de Chimie Organique, Université de Genève, quai Ernest Ansermet 30, CH-1211 Genève 4, Switzerland