1. Department of Chemistry, Zhejiang University, Hangzhou 310027, China, College of Bioengineering, Chongqing University, Chongqing 400044, China, Department of Biological and Chemical Engineering, Chongqing Education College, Chongqing 400067, China, and Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611