Kawai, Kiyohiko; Sugimoto, Akira; Yoshida, Hiroko; Tojo, Sachiko; Fujitsuka, Mamoru; Majima, Tetsuro Bioorganic and Medicinal Chemistry Letters, 2005, vol. 15, # 20 p. 4547 - 4549 doi: 10.1016/j.bmcl.2005.07.004