1. Department of Organic Chemistry, NSRIM, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands, DSM Research, Life SciencesAdvanced Synthesis, Catalysis and Development, P.O. Box 18, 6160 MD Geleen, The Netherlands, and Chiralix B.V., Toernooiveld 100, 6525 EC Nijmegen, The Netherlands