A new approach to the synthesis of indole-and benzofuran-containing tetracyclic condensed systems

A new method is described for the synthesis of the 1H-benzo[b]furoindole heterocyclic systems from the corresponding isomeric amino acids with amino groups at positions 2 and 3. By this method it is possible to obtain these tetracyclic systems not only in the form of one isomer but also to convert them from one to the other. From the tetracyclic systems with angular structure it is possible to obtain the corresponding linear isomers. On the other hand, from the isomer with the linear structure it is possible to change to the isomer with angular fusion of the pyrrole ring. The classical Fischer reaction served as model for such transformations. © 2007 Springer Science+Business Media, Inc.