Oscar R. Suárez-Castillo, Lidia Beiza-Granados, Myriam Meléndez-Rodríguez, Alejandro Alvarez-Hernandez, Martha S. Morales-Rios and Pedro Joseph-Nathan. Synthesis of Bromoindole Alkaloids from Laurencia brongniartii Journal of Natural Products. 2006, 69, 1596-1600. ISSN 0163-3864. The American Chemical Society. Estados Unidos de América.
A regioselective synthesis of N-carbomethoxy-2,3,5-tribromoindole (6) via a sequential one-pot bromination?aromatization?bromination of N-carbomethoxyindoline (2) is described. The process for the transformation of 2 into 6 permitted the isolation of stable reaction intermediates N-carbomethoxy-5-bromoindoline (3), N-carbomethoxy-5-bromoindole (4), and N-carbomethoxy-3,5-dibromoindole (5). Compound 6 was used to complete the total synthesis of the natural products 1b and 1c. In addition, bromination of N-carbomethoxyindole (11) afforded N-carbomethoxy-2,3,6-tribromoindole (13), from which the natural product 1a was synthesized.