1. Key Laboratory of Marine Drugs, Ministry of Education; Molecular Synthesis Center, and School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, P. R. China
2. Laboratory for Marine Drugs and Bioproducts, Qingdao Marine Science and Technology Center, Qingdao, 266237, P. R. China
3. College of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, P. R. China
4. Laoshan Laboratory, Qingdao 266237, P. R. China