Sole, Daniel; Garcia-Rubio, Silvina; Bosch, Joan; Bonjoch, Josep
Heterocycles, 1996 , vol. 43, # 11 p. 2415 - 2424

Nishiyama, Takashi; Esumi, Tomoyuki; Iwabuchi, Yoshiharu; Irie, Hiroshi; Hatakeyama, Susumi
Tetrahedron Letters, 1998 , vol. 39, # 1-2 p. 43 - 46