1. College of Pharmacy, Oregon State University, Corvallis, Oregon 97331, School of Chemistry, University of Bristol, Bristol, BS8 ITS U.K., Life Sciences Institute, Department of Medicinal Chemistry, Department of Chemistry, and Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan 48109, and Scripps Institution of Oceanography and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California 92093