1. Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, Chemistry Research Laboratories, Dainippon Sumitomo Pharma Company, Ltd., 33-94, Enoki, Suita, Osaka 564-0053, Japan, and Chemical Synthesis Laboratories, Technology Research & Development Center, Dainippon Sumitomo Pharma Company, Ltd., 3-1-98, Kasugade Naka, Konohana-ku, Osaka 554-0022, Japan