1. Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Sendai 980-8578, Japan, Faculty of Pharmaceutical Sciences, Okayama University, Tsushima, Okayama 700-8530, Japan, and Ashigara Research Laboratories, Fuji Photo Film Company, Ltd., 210 Nakanuma, Minamiashigara, Kanagawa 250-0193, Japan