Synthesis 2009(10): 1667-1672  
DOI: 10.1055/s-0028-1088050
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of the Reported Protoberberine Gusanlung D

Prasad B. Wakchaure, Srinivasan Easwar, Narshinha P. Argade*
Division of Organic Chemistry, National Chemical Laboratory, Pune 411008, India
e-Mail: np.argade@ncl.res.in;
Further Information

Publication History

Received 15 January 2009
Publication Date:
20 April 2009 (online)

Abstract

Starting from homopiperonylamine or phenethylamine with homophthalic anhydride or 3,4-methylenedioxyhomophthalic acid, respectively, facile syntheses of the reported structures of (±)-gusanlung D and (±)-isogusanlung D were accomplished via regioselective­ reductive dehydration of the corresponding homophthalimides followed by an intramolecular acid-catalyzed or radical cyclization pathway. Starting from the corresponding suitably ortho-halogenated homophthalimides, the syntheses of dehydrogusanlung and dehydroisogusanlung D were completed via regioselective reductive dehydration followed by an intramolecular Heck coupling reaction as the key steps. The analytical and spectral data obtained for all four synthetic compounds differed from the reported data for natural gusanlung D, and therefore the structural assignment of the natural product needs to be revised.