1. Department of Chemistry; Rice University; 6100 Main Street Houston TX 77005 USA
2. Department of Chemistry & Biochemistry; University of California, San Diego; 9500 Gilman Drive La Jolla CA 92093 USA
3. Department of Chemistry; The Scripps Research Institute; 10550 North Torrey Pines Road La Jolla CA 92037 USA
4. Screening Technologies Branch, Developmental Therapeutics Program; Division of Cancer Treatment and Diagnosis; Frederick National Laboratory for Cancer Research; National Cancer Institute; National Institutes of Health; Frederick MD 21702 USA