Occurrence of Phenylpyruvic Acid in Woody Plants: Biosynthetic Significance and Synthesis of an Enolic Glucoside Derivative.

The leaves and stems of Aspalathus linearis, a member of the Fabaceae, contains (Z)-2-(β-D-glucopyranosyloxy)-3-phenylpropenoic acid 1, an enolic glucoside of phenylpyruvic acid, representing the first unequivocal evidence for the latter's presence in woody plants. The synthesis of a derivative 2 of the natural product, and of related regiomeric and geometrical isomers 3,4 and 5, and the biosynthetic significance in relation to the shikimic acid pathway are discussed.