1. Drug Discovery Program, Department of Medicinal Chemistry and Pharmacognosy, University of Illinois at Chicago, 833 South Wood, Chicago, Illinois 60612, Burke Medical Research Institute, 785 Mamaroneck Avenue, White Plains, New York 10605, and Dipartimento di Scienze Farmaceutiche “Pietro Pratesi”, Università degli Studi di Milano, Via Mangiagalli 25, I-20133 Milan, Italy