1. Department of Chemistry, Southeast Missouri State University, Cape Girardeau, Missouri 63701
2. Drug Development Laboratory, University of Kansas Cancer Center, University of Kansas Medical Center, Kansas City, Kansas 66160‐7419
3. Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160‐7419
4. Department of Chemistry, University of California, Berkeley, California 94720