1. School of Molecular Biosciences, Washington State University, Pullman, Washington, 99164, Meiji Seika Kaisha, Ltd., Pharmaceutical Research Center, Pharmacokin, 760 Morooka-cho, Kohoku-ku, Yokohama, Japan 222-8567, Department of Medicinal Chemistry, University of Washington, Box 357610, Seattle, Washington 98195-7610, and Department of Chemistry, Washington State University, P.O. Box 644630, Pullman, Washington 99164-4630