1. The MRC Glycosciences Laboratory, Northwick Park Hospital, Watford Road, Harrow, Middlesex, HA1 3UJ, U.K., MRC Biomedical Nuclear Magnetic Resonance Centre, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, U.K., Institute of Biomolecular Sciences, School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, Scotland, U.K., and Laboratoire de Chimie Organique Multifonctionnelle, Université de ParisSud, Bat. 420, 91405 Orsay Cedex, France