Su, Chung-Ren; Shen, Yuh-Chiang; Kuo, Ping-Chung; Leu, Yann-Lii; Damu, Amooru G.; Wang, Yea-Hwey; Wu, Tian-Shung Bioorganic and Medicinal Chemistry Letters, 2006 , vol. 16, # 24 p. 6155 - 6160