1. Natural Products Laboratory, School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, Faculty of Pharmacy, Meijo University, Tempaku, Nagoya 468-8503, Japan, Tokai Gakuen University, Miyoshi, Aichi 470-0207, Japan, and Niigata College of Pharmacy, Kamishin'ei-cho, Niigata 950-2081, Japan