1. Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K., School of Biomedical Sciences, Institute of Cell and Molecular Biosciences, University of Newcastle, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, U.K., and Centre for Carbohydrate Chemistry, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, U.K.