1. Center of Pharmaceutical Informatics, Department of Pharmacy, Uppsala University, Uppsala Biomedical Center, P.O. Box 580, SE-751 23 Uppsala, Sweden, Department of Medicinal Chemistry, AstraZeneca Research and Development, SE-151 85 Södertälje, Sweden, and Department of Chemistry, Medicinal Chemistry, Göteborg University, SE-412 96 Göteborg, Sweden