Atsuumi, Shugo; Nakano, Masato; Koike, Yutaka; Tanaka, Seiichi; Ohkubo, Mitsuru; Yonezawa, Toshiko; Funabashi, Hiroshi; Hashimoto, Junko; Morishima, Hajime Tetrahedron Letters, 1990 , vol. 31, # 11 p. 1601 - 1604