Unusual rearrangements and cyclizations involving polycyclic indolic systems

Unusual rearrangements and cyclizations involving polycyclic indolic systems Alamdar Ashnagar,1a Patrick D. Bailey,* Philip J. Cochrane,1b Timothy J. Mills, and Richard A. Price School of Chemistry (Faraday Building), The University of Manchester, Sackville Street, Manchester, M60 1QD, UK Email: [email protected] Abstract During the course of experiments to explore and develop cyclization reactions of indolic systems, a number of unusual rearrangement reactions were discovered, and are reported in this paper. We describe routes to 4-substituted (methylsufanylmethyl)indole derivatives, and a simple route to a cyclopropanone derivative of a tetrahydro-ß-carboline. Keywords: Indole, Sommelet-Hauser rearrangement, Pictet-Spengler reaction, cyclopropanone Introduction There are an enormous number of important indolic natural products, containing a plethora of fused ring systems, as exemplified below (Figure 1). Our interest has been in using tryptophan as the chiral starting material for the synthesis of such compounds,2 and in developing synthetic methods for accessing the polycyclic structures.3 NHNOHOLysergic Acid 1H NHNNHOOHHOBrevianamide E 2NHNNNOHHOOHOkaramine A 4NNHOHAjmaline 3OH Figure 1