The Design and Synthesis of Inhibitors of Imidazoleglycerol Phosphate Dehydratase as Potential Herbicides

The discovery and exploration of a new class of broad-spectrum post-emergent herbicides with a novel mode of action, namely the disruption of histidine biosynthesis via inhibition of imidazoleglycerol phosphate dehydratase (IGPD; E.C. 4.2.1.19), are described. Clear structural similarities between the first member, produced during an attempt to produce analogues of glyphosate, and intermediates in histidine biosynthesis were noted. Several series of targets were designed, to mimic both the enzyme substrate and a putative reaction intermediate, and synthesised. Some examples were found to be both extremely potent inhibitors of the enzyme, having K_i values as low as 0·3 nM , and phloem-mobile herbicides with levels of weed control similar to those shown by glyphosate. Further logical progress awaits a high-resolution X-ray structure determination of an enzyme-inhibitor complex. © 1997 SCI