1. Department of Organic Pharmaceutical Chemistry, Uppsala Biomedical Center, Uppsala University, Box 574, S-751 23 Uppsala, Sweden, Department of Biochemistry, Uppsala Biomedical Center, Uppsala University, Box 576, S-751 23 Uppsala, Sweden, Department of Molecular Biology, Uppsala Biomedical Center, Uppsala University, Box 590, S-751 24 Uppsala, Sweden, Department of Chemistry, Linköping University, S-581 83 Linköping, Sweden, Medivir AB, Lunastigen 7, S-141 44 Huddinge, Sweden, and Department of Organic...