1. Division of Organic Chemistry, National Institute of Health Sciences, Kanagawa 210-9501, Japan
2. Graduate School of Medical Life Science, Yokohama City University, Kanagawa 236-0027, Japan
3. Graduate School of Pharmacy, Showa University, Tokyo 142-8555, Japan
4. Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan