1. Laboratory of Aquatic Natural Products Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
2. Misaki Marine Biological Station (MMBS), Graduate School of Science and Center for Marine Biology, The University of Tokyo, Misaki, Miura, Kanagawa 238-0225, Japan
3. Sugashima Marine Biological Laboratory, Graduate School of Science, Nagoya University, Toba, Mie 517-0004, Japan