1. Department
of Chemistry, Colorado State University, Fort Collins, Colorado 80524, United States
2. Graduate
School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan
3. Life Sciences Institute and Departments of Medicinal Chemistry, Microbiology & Immunology, and Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
4. University of Colorado Cancer Center, Aurora, Colorado 80045, United States