1. Department of Pharmacochemistry, Division of Medicinal Chemistry, Leiden/Amsterdam Center for Drug Research, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands, and Gorlaeus Laboratories, Division of Medicinal Chemistry, Leiden/Amsterdam Center for Drug Research, Universiteit Leiden, P.O. Box 9502, 2300 RA Leiden, The Netherlands