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

Abstract

2-Methyl-5-(tert-butyldimethylsilyloxy)phenyl N, N, N', N'-tetramethylphosphorodiamidate was lithiated with sec-BuLi in the presence of N, N, N', N'-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.