Beflubutamid is a chiral herbicide against dicotyledonous weeds in cereals. The racemic compound is applied although only the S-enantiomer is herbicidally active. Enantiomers may also differ with respect to plant metabolism, environmental fate, and (eco)toxicity. Therefore, replacement of racemic by enantiomer-enriched compounds should be considered as it may lower application rates, residues in crops and environment, and side effects on nontarget organisms. In soils, beflubutamid is degraded to an amide and acid metabolite that are still chiral. In this study, degradation of beflubutamid and sequential formation and degradation of these metabolites were followed with laboratory incubation experiments using racemic compounds and also pure enantiomers that were prepared from racemic standards using enantioselective HPLC-separation. The compounds were analyzed with chiral GC-MS. Incubation studies with pure enantiomers showed that beflubutamid and the amide metabolite were both configurationally stable, whereas for the acid, enantiomerization was observed. Degradation was enantioselective, particularly for the amide.

Degradation of the chiral herbicide beflubutamid in soil: Enantioselectivity, enantiomerization, and formation/degradation of chiral metabolites

243rd National Meeting (2012)

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