1. Laboratory of Aquatic Natural Products Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan, Aquatic Resources Research Institute, Chulalongkorn University, Bangkok 10330, Thailand, Prince of Songkla University, Suratthani Campus, Suratthani 84000, Thailand, and Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand