1. Natural Products Laboratory, School of Pharmacy, University of North Carolina, North Carolina 27599, Graduate Institute of Natural Products, Kaohsiung Medical College, 100 Shih Chuan 1st Road, Kaohsiung, Taiwan, College of Food Engineering, State University of Campinas (UNICAMP), 13081-970, Caixia Postal 6177, Campinas, SP. Brazil, and Panacos Pharmaceuticals, 217 Perry Parkway, Gaithersburg, Maryland 20877