Regiospecific synthesis of mono-N-substituted indolopyrrolocarbazoles
Wolfgang Fröhner1, Barbara Monse, Tobias M Braxmeier
1Chemistry Department, Sirenade Pharmaceuticals AG, Am Klopferspitz 19a, D-82152 Martinsried, Germany.
Abstract:
[reactions: see text] Two complementary and efficient strategies have been developed for the regiospecific synthesis of unsymmetrical indolopyrrolocarbazoles (IPCs) mono-N-substituted with a pentacycle. A halogen in position 2 of the intermediate bisindolylmaleimides 3a-e allows a selective Mitsunobu coupling by exploiting the increased acidity of the 2-chloro-substituted indole nitrogen. It also promotes an easier cyclization of bisindolylmaleimides 4a-e and 7b-e to IPCs. Alkylation of the 2-unsubstituted indole-3-carboxamides 2a,b and further processing to the corresponding IPCs gives access to the opposite regioisomers.
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