1. University of Groningen, Department of Chemical Engineering, Nijenborgh 4, 9747 AG Groningen, The Netherlands, DSM Pharmaceutical Products, Innovative Synthesis and Catalysis, P.O. Box 16, 6160 MD Geleen, The Netherlands, and University of Groningen, Stratingh Institute for Chemistry, Nijenborgh 4, 9747 AG Groningen, The Netherlands