Yen, Chiao-Ting; Nakagawa-Goto, Kyoko; Hwang, Tsong-Long; Morris-Natschke, Susan L.; Bastow, Kenneth F.; Wu, Yang-Chang; Lee, Kuo-Hsiung
Bioorganic and Medicinal Chemistry Letters, 2012 , vol. 22, # 12 p. 4018 - 4022

Grover et al.
Journal of the Chemical Society, 1955 , p. 3982,3984