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Synthesis 2004(15): 2499-2504  
DOI: 10.1055/s-2004-831213
PAPER
© Georg Thieme Verlag Stuttgart · New York

Total Synthesis of the Natural Carbazoles Murrayanine and Murrayafoline A, Based on the Regioselective Diels-Alder Addition of exo-2-Oxazolidinone Dienes

Adriana Benavides, Javier Peralta, Francisco Delgado, Joaquín Tamariz*
Departamento de Química Orgánica, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional., Prol. Carpio y Plan de Ayala, 11340 México, Mexico
Fax: +52(55)53963503; e-Mail: jtamariz@woodward.encb.ipn.mx;
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Publication History

Received 21 May 2004
Publication Date:
02 September 2004 (online)

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Abstract

A new synthesis of the natural carbazoles Murrayanine (1) and Murrayafoline A (3) is described. The key step in the synthetic route involved the regioselective cycloaddition of the diene 4,5-dimethylene-3-phenyl-1,3-oxazolidin-2-one (4) to acrolein (6) catalyzed by Lewis acids at low temperature. Direct aromatization of the substituted cyclohexene moiety of adduct 7, and further hydrolysis of the 2-oxazolidinone ring, proved to be a more efficient strategy than the opposite synthetic sequence for the preparation of the corresponding arylphenylamines 14 and 18. Palladium-promoted cyclization of the latter furnished the desired carbazoles 1 and 3 in high overall yields.

Key words

4,5-dimethylene-2-oxazolidinone dienes - murrayanine - murrayafoline A - Diels-Alder - palladium acetate