BIOSYNTHESIS OF THE 2-ARYLBENZOFURAN PHYTOALEXIN VIGNAFURAN IN VIGNA-UNGUICULATA

Feeding experiments using l-phenylalanine-[U-14C], dl-phenylalanine-[1-14C] and -[2-14C] together with degradative studies have been used to investigate the biosynthesis of the 2-arylbenzofuran phytoalexin vignafuran in UV-treated seedlings of cowpea (Vigna unguiculata). During the biosynthetic process, C-3 of phenylalanine appears to be lost, and the resulting labelling pattern is consistent with vignafuran being derived from an isoflavonoid precursor, but the phenylalanine-derived aromatic ring becomes the 2-aryl substituent and not part of the benzofuran system. A previously proposed pathway to 2-arylbenzofurans by loss of C-6 from a coumestan is thus excluded. Alternative routes are suggested. © 1979.