Diez-Barra, Enrique; De la Hoz, Antonio; Loupy, Andre; Martinez-Gonzalez, Alfonso; Martinez-Merino, Victor; Merino, Sonia; Paugam, Renee; Sanchez-Verdu, Prado; Sansoulet, Jean; Torres, Jose Tetrahedron, 1997 , vol. 53, # 10 p. 3659 - 3668