Stereoselective Degradation and Microbial Epimerization of Triadimenol in Soils

Triadimenol is a widely used triazole fungicide and consists of four stereoisomers with 1R,2S, 1S,2R, 1R,2R, and 1S,2S configurations. The trans‐enantiomeric pair (1R,2S‐isomer and 1S,2R‐isomer) is also called triadimenol‐A and the cis‐enantiomeric pair (1R,2R‐isomer and 1S,2S‐isomer) triadimenol‐B. In this study, the stereoselective degradation and chiral stability of triadimenol in two soils were investigated in details. The dissipation of technical triadimenol, a 6:1 mixture of triadimenol‐A and triadimenol‐B, showed significant epimerization from triadimenol‐A to triadimenol‐B occurred along with the dissipation process. The degradation exhibited some stereoselectivity, resulting in a concentration order of 1S,2S > 1R,2R > 1R,2S > 1S,2R or 1S,2S > 1R,2R > 1S,2R > 1R,2S at the end of the 100 days incubation for Baoding soil or Wuhan soil, respectively. Further incubation of triadimenol‐B revealed no epimerization, i.e. triadimenol‐B was configurationally stable in soil, and 1R,2R‐triadimenol degraded slightly slower in the former part and slightly faster in the later part of the incubation than 1S,2S‐triadimenol. Moreover, by incubation of enantiopure 1S,2R‐triadimenol and 1R,2S‐triadimenol, the results documented the epimerization for each enantiomer occurred at both C‐1 and C‐2 positions. Finally, the present work also documented that the enantiomerization reaction for all the four stereoisomers was nearly negligible in the soils. Chirality 25:355‐360:, 2013. © 2013 Wiley Periodicals, Inc.