Metalaxyl
Metalaxyl is an acylalanine fungicide with systemic function.[1] Its chemical name is methyl N-(methoxyacetyl)-N-(2,6-xylyl)-DL-alaninate. It can be used to control Pythium in a number of vegetable crops, and Phytophthora in peas. Metalaxyl-M is the ISO common name[2] and Ridomil Gold is the trade name for the optically pure (-) / D / R active stereoisomer, which is also known as mefenoxam.[3]
It is the active ingredient in the seed treatment agent Apron XL LS.[4]
The fungicide has suffered severe <templatestyles src="Template:Visible anchor/styles.css" />resistance problems. The fungicide was marketed for use against Phytophthora infestans. However, in the summer of 1980, in the Republic of Ireland, the crop was devastated by a potato blight epidemic after a resistant race of the oomycete appeared.[5] Irish farmers later successfully sued the company for their losses.Script error: No such module "Unsubst". Maximum pesticide residue limits for the EU/UK are set at 0.5 mg/kg for oranges and 1.0 mg/kg for apples.Script error: No such module "Unsubst". As early as 1998 Pythium was known to be widely developing resistance to metalaxyl[6] which was the most effective control at the time.[6] Various Pythium populations have been known to have resistance to mefenoxam since the 1980s[7] and metalaxyl since 1984.[8] There is wide variability in resistance/sensitivity between Pythium species, with some populations showing complete ineffectiveness.[7]
Synthesis
The first synthesis of metalaxyl was disclosed in patents filed by Ciba Geigy.[9]
2,6-Xylidine is alkylated with methyl 2-bromopropionate to give an alanine derivative. This is further reacted with the acid chloride of methoxyacetic acid to yield racemic metalaxyl.[9][10] The homochiral, single-isomer version of the chemical, which retains all its fungicidal activity, has been manufactured.[11]
References
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- ↑ Working on potato blight in Northern Ireland
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