1. Department of Pharmacology and Toxicology, Division of Medicinal and Natural Products Chemistry, College of Pharmacy, University of Arizona, 1703 E. Mabel Street, Tucson, Arizona 85721, Wyeth Research, Natural Products Sourcing, 401 N. Middletown Road, Pearl River, New York 10965, and Instituto de Recursos Biologicos, Las Cabanas y Los Reseros s/n, 1712 Villa Udaondo−Castelar, Provincia de Buenos Aires, Argentina