1. Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, Japan, and Medicinal Chemistry Research Laboratories, Pharmaceutical Research Center, Meiji Seika Kaisha, Ltd., 760 Morooka-cho, Kohoku-ku, Yokohama 222-8567, Japan