1. School of Pharmacy; University of Wisconsin-Madison; Madison, WI 53705 USA
2. School of Pharmaceutical Science and Technology; Tianjin University; Tianjin 300072 P. R. China
3. Department of Chemistry; University of Wisconsin-Madison; Madison, WI 53706 USA
4. School of Biological and Chemical Engineering; Zhejiang University of Science and Technology; Hangzhou 310023 P. R. China
5. Key Laboratory of Marine Drugs; Chinese Ministry of Education; School of Medicine and Pharmacy; Ocean University of China; Qingdao 266003 P. R. China.