1. AstraZeneca Pharmaceuticals, Department of Medicinal Chemistry R&D, Södertälje, S-151 85, Sweden, AstraZeneca, Process R&D Avlon/Charnwood, Avlon Works, Severn Road, Hallen, Bristol, BS10 7ZE, U.K., and Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA, U.K.