1. Department of Molecular Design and Synthesis, Division of Pharmaceutical Chemistry, Institute of Health Biosciences, The University of Tokushima, 1-78, Sho-machi, Tokushima 770-8505, Japan, and Department of Chemistry, Faculty of Integrated Arts and Sciences, The University of Tokushima, 1-1, Minamijosanjima-cho, Tokushima 770-8502, Japan