1. Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, National Institutes of Health, P.O. Box 12233 Research Triangle Park, NC, 27709, U.S.A.
2. Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, 94143-0446, U.S.A.
3. Children's Hospital Oakland Research Institute, Oakland, CA, U.S.A.