Synthesis 2007(13): 1943-1948  
DOI: 10.1055/s-2007-983741
PAPER
© Georg Thieme Verlag Stuttgart · New York

exo-2-Oxazolidinone Dienes in the Total Synthesis of the Natural Carbazoles, 6-Methoxymurrayanine and Clausenine

Pablo Bernal, Adriana Benavides, Rafael Bautista, Joaquín Tamariz*
Departamento de Química Orgánica, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional. Prol., Carpio y Plan de Ayala, 11340 México, D. F. México
Fax: +52(5)557296300/46211; e-Mail: jtamariz@woodward.encb.ipn.mx;
Further Information

Publication History

Received 21 February 2007
Publication Date:
18 June 2007 (online)

Abstract

A new application of exo-2-oxazolidinone dienes in the regioselective synthesis of natural carbazoles, 6-methoxymurrayanine (6) and clausenine (7), is described. The regioselective cycloaddition of novel diene 10 to acrolein by Lewis acid catalysis provided adduct 12, which after aromatization gave benzoxazolone 14 as the key intermediate for the preparation of both carbazoles. A straightforward and efficient synthesis of 7 was carried out by a procedure with no isolation of intermediates, starting from 14 and went through a sequence of hydrogenation-hydrolysis-methylation and Pd-cyclization to give the desired carbazole 7 in high overall yield.