[Development of synthetic methods for 4-substituted indoles and their applications for the syntheses of natural products].

In our continuing work on synthesizing 4-substituted indole alkaloids as simple as possible by creating suitable reactions, we developed synthetic methods for 4-substituted indoles having a nitrogen or oxygen functional group at the 4-position starting from indole-3-carbaldehyde and one step conversion method of indole-3-carbaldehydes into indole-3-acetonitriles. Utilizing them, we could establish a practical synthetic route to 1,3,4,5-tetrahydropyrrolo[4,3,2-de]-quinoline in three steps from indole-3-carbaldehyde. On the basis of these results, short step total syntheses of marine indole alkaloids, such as isobatzelline C, batzelline C, makaluvamine A, and damirones A and B, were achieved. Furthermore, a novel preparative method of psilocin was established in only five steps from indole-3-carbaldehyde. The syntheses of psilocin analogs having a formyl group or bromine in the benzene part were also achieved.