1. Organic Chemistry 2, Center for Chemistry and Chemical Engineering, Lund Institute of Technology, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden, Active Biotech, Lund Research Center, P.O. Box 724, SE-220 07 Lund, Sweden, and Organic Chemistry, Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden