1. Department of Pharmaceutical Chemistry, School of Pharmacy, and Department of Medicine, School of Medicine, University of California, San Francisco, CA 94143.
2. Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, CA 94143.
3. Cancer Research Institute and Department of Pediatrics, University of California, San Francisco, CA 94143.
4. Veterans Administration Hospital, White River Junction, VT 05001, and Department of Medicine, Dartmouth Medical School, Hanover, NH 03756.
5. Department of Medicine, Dartmouth Medical School, Hanover, NH 03756.