Cho, Nobuo; Nara, Yoshi; Harada, Mioko; Sugo, Tsukasa; Masuda, Yasushi; Abe, Akemi; Kusumoto, Keiji; Itoh, Yasuaki; Ohtaki, Tetsuya; Watanabe, Toshifumi; Furuya, Shuichi Chemical and Pharmaceutical Bulletin, 1998, vol. 46, # 11 p. 1724 - 1737