1. Laboratory of Organic Chemistry, Natural Products Chemistry Group, Wageningen University, Dreijenplein 8, 6703 HB Wageningen, The Netherlands, Department of Environmental Sciences, Wageningen University, P.O. Box 342, 6700 AH Wageningen, The Netherlands, Bruker Biospin GmbH, D-76287 Rheinstetten, Germany, and Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, 85721 Tucson, Arizona