Synthetic Study of Naturally Occurring Indoles Possessing Various Substituents on Benzene Moiety.

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A new synthetic methodology of indole nucleus starting with ethyl pyrrole-2-carboxylate (1) and its application were examined as follows.1. The C_4-acylation of 1 by Friedel-Crafts reaction was examined, and the scope and limitation were established (1 -> 2). On the basis of it, a new synthetic route for indoles possessing various substituents on benzene moiety was developed.2. By applying the above method, the synthesis of 9-methoxybenz[f] indole (6) was successful, and naturally occurring eupolauramine (7) was synthesized from 6.3. Regioselectivity was found in the bromination of a methoxyindole derived from 1, and thus the regioselective bromination was systematically carried out on various methoxyindoles.4. A synthesis of naturally occurring hymenin (11) from marine sponge was examined, and we have obtained the intermediate compound 14 at the present time.