1. CCNU-uOttawa Joint Research Centre, Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry; Central China Normal University; 152 Luoyu Road, Wuhan Hubei 430079 P. R. China
2. Department of Chemistry and Biochemistry; University of California; Los Angeles California 90095 USA
3. State Key Laboratory of Applied Organic Chemistry; Lanzhou University; Lanzhou 730000 P. R. China