1. Department of Medicinal Chemistry Tokyo University of Pharmacy and Life Sciences Hachioji Tokyo 192-0392 Japan
2. Present address: Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology Tokyo 152-8552 Japan
3. Department of Chemistry and Bioscience Graduate School of Science and Engineering Kagoshima University Korimoto Kagoshima 890-0065 Japan
4. Present address Department of Environmental Biochemistry Kyoto Pharmaceutical University Kyoto 607-8414 Japan