1. IMM Solid State Chemistry, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, Netherlands, Department of Chemistry and Department of Chemical Engineering, Imperial College, London SW7 2AZ U.K., DSM Pharmaceutical ProductsAdvanced Synthesis, Catalysis & Development, P.O. Box 18, 6160 MD Geleen, Netherlands, and Syncom B.V., Kadijk 3, 9747 AT Groningen, Netherlands