Takahashi, Masami; Kuroda, Tooru; Ogiku, Tsuyosi; Ohmizu, Hiroshi; Kondo, Kazuhiko; Iwasaki, Tameo Tetrahedron Letters, 1991, vol. 32, # 47 p. 6919 - 6922 doi: 10.1016/0040-4039(91)80444-B