1. Department of Chemistry, Lash Miller Chemical Laboratories, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6, Institute of Pharmaceutical Chemistry, University of Szeged, Eötvös u. 6., H-6720 Szeged, Hungary, and Department of Medicinal Chemistry, University of Szeged, Dom ter 8, 6720 Szeged, Hungary