Transformation of 14C-pyrimidynyloxybenzoic herbicide ZJ0273 in aerobic soils

A soil metabolism study of propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate (ZJ0273), a novel broad-spectrum herbicide, was carried out using C-14 labeled on two different rings, i e., [pyrimidine-4,6-C-14] ZJ0273 and [benzyl-U-C-14] ZJ0273 Ultralow liquid scintillation counting and LC-MS/MS were used to identify the degradation intermediates and quantify their dynamics in aerobic soils. Four aromatic intermediates, 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoic acid (M1), 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzamido)benzoic acid (M2), 2-(4,6-dimethoxypyrimidin-2-yloxy)benzoic acid (M3). and 4,6-dimethoxypyrimidm-2-ol (M4). were identified and their identity was further confirmed against authentic standards Analysis of metabolites suggested two degradation pathways (1) Upon loss of the propyl group. M1 was produced via hydrolysis of propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy) benzylamino)benzoate after which the C-N bond between rings A and B was cleaved by oxidation and biochemical degradation to yield M3. which was further converted into M4 and finally mineralized to CO2, and (2) the first step was the same as in pathway I, but M1 first underwent a carbonylation to form M2. The C-N bond between rings A and B of M2 was cleaved by hydrolysis to yield M3 Dynamic changes in the four metabolites in aerobic soils were also investigated by HPLC coupled analysis of radioactivity of isolated peaks. After a 100-day incubation. 1 7-9 7% of applied C-14 was found as M1, 0 3-1 1% as M2, 14 5-20 9% as M3, and 3 7-6 7% as M4 in the soils, and pH appeared to be the most influential soil property affecting the formation and dissipation of these metabolites. (C) 2010 Elsevier B V All rights reserved