Studies on the synthesis of the azocino[4,3-b]indole framework and related compounds

An efficient method for the synthesis of C-4 position alkylated azocino[4,3-b]indole 13 and 18 is described. Reduction of compounds 5, 6, 7 and 8 yielded the corresponding alcohols. Compounds 5, 6, 7 and 8 were synthesized through several steps starting from 1. The resulting alcohols underwent acid catalyzed ring closure to give tetracyclic azocino[4,3-b]indole 9, 10, 11 and 12. Finally, compounds 9 and 17 were alkylated at C-4 position to the corresponding products 13 and 18. The structure of the compounds 13 and 18 has been confirmed by X-ray single crystal analysis.