1. Graduate School of Human Informatics, Nagoya University, Chikusa, Nagoya 464-8601, Japan, Department of Physics, Graduate School of Science, Kyoto University, and CREST (Core Research for Evolutional Science and Technology) of Japan Science and Technology Corporation, Sakyo, Kyoto 606-8502, Japan, and Laboratoire de Chimie Organique des Substances Naturelles associé au CNRS, Centre de Neurochimie, Université Louis Pasteur, 5 rue Blaise Pascal, 67084 Strasbourg, France