Metalaxyl is an acylalanine

fungicide Fungicides are pesticides used to kill parasitic fungi or their spores. Fungi can cause serious damage in agriculture, resulting in losses of yield and quality. Fungicides are used both in agriculture and to fight fungal infections in animals, ...

with systemic function. 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 Vegetables are edible parts of plants that are consumed by humans or other animals as food. This original meaning is still commonly used, and is applied to plants collectively to refer to all edible plant matter, including edible flower, flo ...

crops, and ''

Phytophthora ''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species cause economic losses on crops worldwide, as well as environmental dam ...

'' in

pea Pea (''pisum'' in Latin) is a pulse or fodder crop, but the word often refers to the seed or sometimes the pod of this flowering plant species. Peas are eaten as a vegetable. Carl Linnaeus gave the species the scientific name ''Pisum sativum' ...

s. Metalaxyl-M is the ISO common name and Ridomil Gold is the trade name for the optically pure (-) / D / R active stereoisomer, which is also known as mefenoxam. It is the active ingredient in the seed treatment agent Apron XL LS. The fungicide has suffered severe problems. The fungicide was marketed for use against ''

Phytophthora infestans ''Phytophthora infestans'' is an oomycete or Oomycete, water mold, a fungus-like microorganism that causes the serious potato and tomato disease known as late blight or potato blight. Early blight, caused by ''Alternaria solani'', is also often c ...

''. However, in the summer of 1980, in the

Republic of Ireland Ireland ( ), also known as the Republic of Ireland (), is a country in Northwestern Europe, north-western Europe consisting of 26 of the 32 Counties of Ireland, counties of the island of Ireland, with a population of about 5.4 million. ...

, the crop was devastated by a potato blight epidemic after a resistant race of the

oomycete The Oomycetes (), or Oomycota, form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms within the Stramenopiles. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction o ...

appeared. Irish

farmer A farmer is a person engaged in agriculture, raising living organisms for food or raw materials. The term usually applies to people who do some combination of raising field crops, orchards, vineyards, poultry, or other livestock. A farmer ...

s later successfully sued the company for their losses. Maximum pesticide residue limits for the EU/UK are set at 0.5 mg/kg for oranges and 1.0 mg/kg for apples. As early as 1998 Pythium was known to be widely developing resistance to metalaxyl which was the most effective control at the time. Various ''Pythium'' populations have been known to have resistance to mefenoxam since the 1980s and metalaxyl since 1984. There is wide variability in resistance/sensitivity between ''Pythium'' species, with some populations showing complete ineffectiveness.

Synthesis

The first synthesis of metalaxyl was disclosed in patents filed by Ciba Geigy. : 2,6-Xylidine is alkylated with methyl 2-bromopropionate to give an

alanine Alanine (symbol Ala or A), or α-alanine, is an α-amino acid that is used in the biosynthesis of proteins. It contains an amine group and a carboxylic acid group, both attached to the central carbon atom which also carries a methyl group sid ...

derivative. This is further reacted with the

acid chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...

of methoxyacetic acid to yield

racemic In chemistry, a racemic mixture or racemate () is a mixture that has equal amounts (50:50) of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as r ...

metalaxyl. The homochiral, single-isomer version of the chemical, which retains all its fungicidal activity, has been manufactured.

References

External links

* * Fungicides Alkyl-substituted benzenes {{mycology-stub