A Short and Convergent Synthesis of the Phytoalexins Vignafuran, 6-Demethylvignafuran, and Moracin M via Directed Lithiation Reaction

Abstract

2-Methyl-5-(tert-butyldimethylsilyloxy)phenyl Ar,JV,Ar7.,/V'-tetrainethylphosphorodiamidate was lithiated with sec-BuLi in the presence of A^A^A^N 'x2018;-tetramethylethylenediamine at —105 °C to generate the corresponding benzylic anion. This benzylic anion was reacted with various methyl benzoates to provide deoxybenzoin derivatives which, without purification, were treated with formic acid to give 2-aryl-6-hydroxybenzo[b]furans. The utility of this strategy has been demonstrated by its application to the short synthesis of phytoalexins, such as vignafuran, 6-demethylvignafuran, and moracin M. © 1991, The Pharmaceutical Society of Japan. All rights reserved.