Imazamox is an imidazolinone herbicide labeled for the control of numerous terrestrial and aquatic weeds. Imazamox was first approved for use on soybeans in 1997 and has received the designation reduced risk pesticide due to low human health impacts, low toxicity to non-target organisms, favorable environmental fate profile, and compatibility with integrated pest management techniques. Carbon-14 labeled imazamox and metabolites are used to evaluate the safety of imazamox in environmental fate and ADME studies. The chemical structure of imazamox affords the possibility to synthesize multiple metabolically stable carbon-14 ring labeled isotopomers, specifically in the imidazolinone and pyridine ring moieties. The carbon-14 custom syntheses of the isotopomeric imazamox, [imidazolinone-5-14C] and imazamox, [pyridine-3-14C], as well as the metabolites CL-354,825 [imidazolinone-5-14C] and CL-312,622, [imidazolinone-5-14C], were successfully completed. The synthesis of imazamox, [imidazolinone-5-14C] is relatively straightforward with a good overall yield starting from potassium cyanide, [14C], while the synthesis of imazamox, [pyridine-3-14C] is more difficult requiring additional synthetic steps in low overall yield starting from sodium acetate, [2-14C]. The synthesis of CL-312,622, [imidazolinone-5-14C] was accomplished by further chemical elaboration of imazamox, [imidazolinone-5-14C]. The synthesis of CL-354,825 [imidazolinone-5-14C] required a re-design of the overall synthetic route and departure from known chemistry to accomplish this more challenging synthesis.

Carbon-14 labeling and synthetic strategies of imazamox and metabolites

256th National Meeting (2018)

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