Morita, Hiroyuki; Takeda, Masahiro; Kamiyama, Hideo; Hashimoto, Tadaaki; Yoshimura, Toshiaki; Shimasaki, Choichiro; Tsukurimichi, Eiichi Tetrahedron Letters, 1996 , vol. 37, # 21 p. 3739 - 3740