Inhibition of Narcissus pseudonarcissus phytoene desaturase by herbicidal 3-trifluoromethyl-1,1 '-biphenyl derivatives

A synthesis program directed to the discovery of novel bleaching herbicides led to the preparation of substituted 3-trifluoromethyl-1,1'-benzoxazoles and 3-trifluoromethyl-1,1'-biphenyls with thiazole-, thiadiazole-, and benz thiazole substituents. Herein, we show that these compounds interfere with the biosynthesis of colored carotenoids by inhibiting the enzyme phytoene d esaturase. IC50 values for inhibition of phytoene desaturase have been dete rmined for 62 derivatives. Several new compounds were found that inhibited phytoene desaturase up to 400-fold more potently than the commercial bleach ing herbicide norflurazon. The derived relationships between chemical struc ture and enzyme inhibition were used to generate a model of the proposed he rbicide binding site. The implication that phytoene desaturase is the targe t site for the substituted 3-trifluoromethyl-1,1'-benzoxazole and biphenyl classes of herbicides is supported by a significant correlation of the IC50 values for inhibition of phytoene desaturase with the biological activity in preemergence upland rests in the greenhouse. (C) 1999 Academic Press.