Triazolopyrimidine sulfonanilide

ALS herbicides. Two classes of ALS-inhibiting herbicides are the sulfonylurea herbicides, discussed in Sections 2.1.2.1 and 2.2.3.1, and the imidazolinone herbicides. A third class of ALS-inhibiting herbicides is the 1,2,4-triazolo [1,5-a]pyrimidine-2-sulfonanilides. The triazolopyrimidine sulfonanilides act by disrupting the biosynthesis of branched chain amino acids in plants. Representatives of this class of herbicides include florasulam (Boxer , Nikos ) [151], initially introduced in Belgium in 1999 and used for the postemergence control of broadleaf weeds in cereals and corn, and flumetsulam (Broadstrike ) [152], used alone or in combination with other herbicides for the control of broadleaf weeds in soybean and corn. 

The triazolopyrimidine sulfonanilides are a class of highly active herbicides. These compounds also act by disrupting the biosynthesis of branched-chain amino acids in plants through the inhibition of AHAS. Cloransulam-methyl, diclosulam, and flor-asulam, as shown in Fig. 11.4, all introduced by Dow AgroSciences, are examples of the triazolopyrimidine sulfonanilide herbicides that contain a fluoro-substituted heterocyclic moiety. 

Triazolopyrimidine sulfonanilide Flumetsulam, florasulam, cloransulam-methyl, diclosulam, metosulam in 6.5 min... 

The metabolism of triazolopyrimidine sulfonanilides (1-4) in plants has been reviewed [23, 24]. It has been shown that diclosulam (3) and doransulam-methyl (4) are rapidly metabolized in soybeans by facile conjugation with homoglutathione which displaces the 7-fluoro substituent (Fig. 2.4.1) [25]. This mechanism was found to only occur in soybeans for 3 and 4. Oxidation at the 4-position of the aniline ring occurs rapidly in maize for 3 and 4. In wheat, 4 undergoes O-dealkylation of 5-ethoxy followed by glucose conjugation and oxidation at the 4-position of the aniline ring occurs for 3 [25]. 

The structure-activity trends for the triazolo[15-a]pyrazines have not been studied as extensively as other members of triazolopyrimidine sulfonanilides [51]. Table 2.4.10 shows the activity on broadleaf and grass species for a series of substitutions on the fused heterocyclic portion of 34. The highest levels of activity on grass and broadleaf species are observed when both 5- and 8-positions are substituted with methoxy (34, R = R = OMe). However, the herbicidal activity observed for 34 is weaker than that for the triazolo[l,5-a]pyrimidine sulfonamides. 

Kleschick WA, Triazolopyrimidine Sulfonanilides and Related Compounds. In Herbicides Inhibiting Branch Chain Amino Acid Biosynthesis, Stetter, J. Ed., Spinger-Verlag, Germany, 1994, Vol. 10, pp 119-143. 

Imidazolinones, diphenyl ethers, sulfonylureas, aryloxyphenoxypropionic acids, triazolopyrimidines, sulfonanilides LC/MS/MS TISP ( + ) (MRM) ngmr level Environmental water... 

Table ni. Characterization of the Response of Susceptible (S) and Resistant (R) Kochia Biotypes to Sulfonylurea, Triazolopyrimidine sulfonanilide, and Imidazolinone Herbicides (adapted from ref. 2. and Saari, L. L. Cotterman, J. C. Primiani, M. M. 1990, Plant Phvsiol. (in press)). 

---