1. Natural Products Chemistry, Division of Applied Biological Chemistry, Graduate School of Agriculture and Biological Sciences, Osaka Prefecture University, 1-1 Gakuencho, Sakai, Osaka 599-8531, Japan, and Fujii Memorial Research Institute, Otsuka Pharmaceutical Co., Ltd., 11-1 1-Chome Karasaki, Otsu, Shiga 520-0106, Japan