1. Bioanalysis and Drug Metabolism, GlaxoWellcome, 5 Moore Drive, Research Triangle Park, North Carolina 27709, Department of Safety of Medicines, Zeneca Pharmaceuticals, Mereside, Alderley Park, Macclesfield, Cheshire SK10 4TG, U.K., and Department of Chemistry, Birkbeck College, University of London, Gordon House, 29 Gordon Square, London WC1H 0PP, U.K.