Ascosonchine, the enol tautomer of 4-pyridylpyruvic acid with herbicidal activity produced by Ascochyta sonchi

A new phytotoxic enol tautomer of 4-pyridylpyruvic acid, named ascosonchine, was isolated from the culture filtrate of Ascochyta sonchi. Such a leaf pathogen is a potential biocontrol agent of Sonchus arvensis, a perennial herbaceous weed occurring throughout the temperate regions of the world. Ascosonchine, characterised as (Z)-2-hydroxy-3-(4-pyridyl)-2-propenoic acid by spectroscopic methods, showed selective herbicidal properties, that are not associated with antibacterial, antifungal or zootoxic activities.