Synthesis of bromoindole alkaloids from Laurencia brongniartii
Oscar R Suárez-Castillo1, Lidia Beiza-Granados, Myriam Meléndez-Rodríguez
1Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Hidalgo, Apartado 1-622, Pachuca, Hidalgo, 42001 México. osuarez@uaeh.edu.mx
Abstract:
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.
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