1. Contribution from Organic Chemistry, Umeå University, S-901 87 Umeå, Sweden, the Department of Cell & Molecular Biology, Section for Medical Inflammation Research, Lund University, P.O. Box 94, S-221 00 Lund, Sweden, and Organic Chemistry 2, Center for Chemistry and Chemical Engineering, Lund Institute of Technology, Lund University, P.O. Box 124, S-221 00 Lund, Sweden