1. Laboratory of Aquatic Natural Products Chemistry, Garaduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyyo-ku, Tokyo 113-8657, Japan, Suntory Institute for Bioorganic Research, 1-1 Wakayamadai, Shimamoto-cho, Osaka 618-0024, Japan, and Zoological Museum of the University of Amsterdam, P.O. Box 94766, 1090 GT Amsterdam, The Netherlands