Yang, Ke-Wu; Cheng, Xu; Zhao, Chuan; Liu, Cheng-Cheng; Jia, Chao; Feng, Lei; Xiao, Jian-Min; Zhou, Li-Sheng; Gao, Hui-Zhou; Yang, Xia; Zhai, Le Bioorganic and Medicinal Chemistry Letters, 2011 , vol. 21, # 23 p. 7224 - 7227