1. Department of Chemistry, P.O. Box 30012, Texas A&M University, College Station, Texas 77842-3012, United States
2. Department of Pharmaceutical Chemistry, University of California, San Francisco, 1700 4th Street, San Francisco, California 94158-2330, United States
3. Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States