1. Medicinal Chemistry Laboratory; Osaka University of Pharmaceutical Sciences; 4-20-1 Nasahara Takatsuki, Osaka 569-1094 Japan
2. Department of Analytical and Bioinorganic Chemistry; Kyoto Pharmaceutical University, 5, Nakauchi-cho, Misasagi; Yamashina-ku Kyoto 607-8414 Japan
3. Medicinal Organic Chemistry Laboratory; College of Pharmaceutical Sciences; Ritsumeikan University, 1-1-1; Noji-higashi Kusatsu, Shiga 525-8577 Japan