1. Center for Marine Natural Products and Drug Discovery, School of Earth and Environmental Sciences; Seoul National University; Seoul 151-747 Korea
2. College of Pharmacy; Yeungnam University; Gyeongsan 712-749 Korea
3. Department of Chemistry and Nano Science, Global Top5 Program; Ewha Womans University; Seoul 120-750 Korea
4. Research Institute of Oceanography; Seoul National University; Seoul 151-747 Korea