1. Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, and Department of Surgical Oncology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, Department of Chemistry, College of Arts and Sciences, Indiana University, Bloomington, Indiana 47405, Department of Chemistry and Biochemistry, College of Letters and Science, Montana State University, Bozeman, Montana 59717, and NaPro BioTherapeutics, Inc., 6304 Spine Road, Boulder, Colorado 80301