Chlorsulfuron structure

Sulfonylureas form a group of selective herbicides. The general structure is given below in Table 7.4. Rj and Rj generally are substituted heterocyclic rings, e.g., 4,6-dimethylpyrimidin-2-yl and 2-(benzoic acid methyl ester) for sulfometuron methyl and 4-methoxy-6-methyl-l,3,5-triazin-2-yl and l-(2-chlorophenyl) for chlorsulfuron, respectively. The compoimds are thermally labile and cannot readily be derivatized and are therefore not amenable to GC-MS. 

General LC/MS Conditions for Sulfonylurea Multiresidue Analysis. We have developed general thermospray LC/MS conditions for the purpose of separating and detecting six different sulfonylurea herbicides. These conditions can be used as a guide fra- a variety of LC/MS residue applications which may require the analysis of one or more of these herbicides. Our procedure includes GLEAN (chlorsulfuron), ALLY (metsulfuron methyl), HARMONY (thiameturon) and EXPRESS cereal herbicides, CLASSIC (chlorimuron ethyl) soybean herbicide and OUST (sulfometuron-methyl) noncrop land herbicide. (Structure 1)... 

Sulfonylurea herbicides (SUHs) are relatively new herbicides, introduced in the 1980s. Chlorsulfuron was the first sulfonylurea marketed in the United States, in 1982. World-wide, 19 sulfonylureas had been commercialized by 1994, and five more are being developed. This rapid increase is due to their very high and specific herbicidal activity, which results in extremely low application rates of 10 to 40 g/ha. Furthermore, as compared to other herbicides, sulfonylureas are less toxic and degrade more rapidly. Chemical structures of some representative sulfonylureas are presented in Figure 25.2. From a chemical point of view, these herbicides are labile and weakly acidic compounds. The common names, chemical formulas, water solubility, pKa, half-life in soil, and leaching potential through the soil (when available) of the most representative sulfonylureas are reported in Table 25.2. 

Assuming that the chlorsulfuron resistance In the A. thallana mutants described here Is due to a mutation within the ALS structural locus. It may be possible to clone the resistant allele. Such a resistance gene should provide a very useful selectable marker for plant transformation studies. Indeed, transfer of the gene to other species may be useful In extending the agronomic utility of the herbicide. 

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