1. Natural Products Laboratory, Division of Medicinal Chemistry and Natural Products, School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, Faculty of Pharmaceutical Science, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-80, Japan, Natural Products Research Center, Kaoshiung Medical College, Kaoshiung, Taiwan, and Niigata College of Pharmacy, 5-13-2 Kamishin'ei-cho, Niigata 950-21, Japan