1. Contribution from the College of Pharmacy, The University of Arizona, 1703 East Mabel, Tucson, Arizona 85721, Department of Chemistry, The University of Arizona, Tucson, Arizona 85721, Cylene Pharmaceuticals, 11045 Roselle Street, Suite C, San Diego, California 92121, and Arizona Cancer Center, 1515 North Campbell Avenue, Tucson, Arizona 85724