Yamamoto, Takeshi; Hori, Manabu; Watanabe, Ikuo; Tsutsui, Hisayoshi; Harada, Kengo; Ikeda, Shoji; Maruo, Joji; Morita, Tominori; Ohtaka, Hiroshi Chemical and Pharmaceutical Bulletin, 1997 , vol. 45, # 12 p. 1975 - 1983