Mandestrobin is a novel strobilurin fungicide registered for the control of a variety of fungal pathogens on canola, grape, strawberry and turf. The registered product is formulated as a 50:50 mixture of R/S stereoisomers. The chiral center of mandestrobin helps define its efficacy and the degradation potential in the environment. Environmental fate studies were designed using three different radiolabeled compounds of mandestrobin - [benzyl-14C]S-2167 (mandestrobin R-isomer, RB), [benzyl-14C]S-2354 (mandestrobin S-isomer, SB), and [phenoxy-14C]S-2167 (mandestrobin R-isomer, RP) to investigate the effect of chirality on degradation in the environment. Chiral HPLC analysis confirmed that specific degradation products were stereospecific (i.e. only a S-isomer degradate was formed). This suggests that the reaction mechanism involves a reaction intermediate that cannot rotate (chiral enzymatic reaction). The effect of chirality on rate of degradation and the formation of unique degradates will be discussed. The experimental conduct and results from several environmental fate studies, including aerobic soil, anaerobic soil, aerobic aquatic and anaerobic aquatic studies will be presented.

Environmental transformation of the chiral agrochemical Mandestrobin

256th National Meeting (2018)

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