Metalaxyl

Metalaxyl is an acylalanine fungicide with systemic function.^[3] 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^[4] and Ridomil Gold is the trade name for the optically pure (-) / D / R active stereoisomer, which is also known as mefenoxam.^[5]

Metalaxyl

Names
IUPAC name Methyl 2-[N-(2,6-dimethylphenyl)(methoxy)acetamido]propanoate
Other names Methyl N-(2,6-dimethylphenyl)-N-(2-methoxyacetyl)alaninate
Identifiers
CAS Number	57837-19-1 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:6790 Y
ChEMBL	ChEMBL105809 Y
ChemSpider	38839 Y
ECHA InfoCard	100.055.418
EC Number	260-979-7
KEGG	C10947 Y
PubChem CID	42586
UNII	16K4M187IF Y
CompTox Dashboard (EPA)	DTXSID6024175
InChI InChI=1S/C15H21NO4/c1-10-7-6-8-11(2)14(10)16(13(17)9-19-4)12(3)15(18)20-5/h6-8,12H,9H2,1-5H3 Y Key: ZQEIXNIJLIKNTD-UHFFFAOYSA-N Y
SMILES COCC(=O)N(c1c(C)cccc1C)C(C)C(=O)OC
Properties
Chemical formula	C15H21NO4
Molar mass	279.33 g/mol
Appearance	Fine white powder
Density	1.20g/cm3 at 20 °C
Melting point	71 to 72 °C (160 to 162 °F; 344 to 345 K)[1]
Boiling point	295.9 °C (564.6 °F; 569.0 K) at 760 mm Hg
Solubility in water	8,400 mg/L at 22 °C
log P	1.65 (octanol/water)[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

It is the active ingredient in the seed treatment agent Apron XL LS.^[6]

The fungicide has suffered severe 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.^[7] Irish farmers later successfully sued the company for their losses.^{[citation needed]} Maximum pesticide residue limits for the EU/UK are set at 0.5 mg/kg for oranges and 1.0 mg/kg for apples.^{[citation needed]} As early as 1998 Pythium was known to be widely developing resistance to metalaxyl^[8] which was the most effective control at the time.^[8] Various Pythium populations have been known to have resistance to mefenoxam since the 1980s^[9] and metalaxyl since 1984.^[10] There is wide variability in resistance/sensitivity between Pythium species, with some populations showing complete ineffectiveness.^[9]

Synthesis

The first synthesis of metalaxyl was disclosed in patents filed by Ciba Geigy.^[11]

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.^[11][12] The homochiral, single-isomer version of the chemical, which retains all its fungicidal activity, has been manufactured.^[13]

References

1. O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. 13th Edition, Whitehouse Station, NJ: Merck and Co., Inc., 2001., p. 1058
2. Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 134
3. Sukul, P; Spiteller, M (2000). "Metalaxyl: persistence, degradation, metabolism, and analytical methods". Reviews of Environmental Contamination and Toxicology. 164: 1–26. PMID 12587832.
4. "Compendium of Pesticide Common Names: metalaxyl". BCPC.
5. Monkiedje, Adolphe; Spiteller, Michael (2002). "Effects of the phenylamide fungicides, mefenoxam and metalaxyl, on the microbiological properties of a sandy loam and a sandy clay soil". Biology and Fertility of Soils. 35 (6): 393–398. doi:10.1007/s00374-002-0485-1. S2CID 22642870.
6. "bmz10s02.pdf" (PDF). Government of Manitoba. Archived from the original (PDF) on 2007-09-30.
7. Working on potato blight in Northern Ireland
8. "Survey of Pythium Isolates for Resistance to Subdue (metalaxyl)" (PDF). UMass Amherst. Retrieved 2020-11-23.
9. Del Castillo Múnera, Johanna; Hausbeck, Mary K. (2016). "Characterization of Pythium Species Associated With Greenhouse Floriculture Crops in Michigan". Plant Disease. 100 (3). American Phytopathological Society: 569–576. doi:10.1094/pdis-03-15-0296-re. ISSN 0191-2917. PMID 30688597.
10. Sanders, P. L. (1984). "Failure of Metalaxyl to Control Pythium Blight on Turfgrass in Pennsylvania". Plant Disease. 68 (1). American Phytopathological Society: 776. doi:10.1094/pd-68-776. ISSN 0191-2917.
11. GB patent 1500581, "Substituted amides and their use as fungicides", issued 1978-02-08, assigned to Ciba-Geigy AG
12. Ishitani, Haruro; Yu, Zhibo; Ichitsuka, Tomohiro; Koumura, Nagatoshi; Onozawa, Shun-ya; Sato, Kazuhiko; Kobayashi, Shū (2022). "Two-Step Continuous-Flow Synthesis of Fungicide Metalaxyl through Catalytic C−N Bond-Formation Processes". Advanced Synthesis & Catalysis. 364: 18–23. doi:10.1002/adsc.202100898.
13. Blaser, Hans-Ulrich; Spindler, Felix (1997). "Enantioselective catalysis for agrochemicals. The case histories of (S)–metolachlor, (R)–metalaxyl and clozylacon". Topics in Catalysis. 4 (3/4): 275–282. doi:10.1023/A:1019164928084.

External links

• Metalaxyl in the Pesticide Properties DataBase (PPDB)
• Metalaxyl-M in the Pesticide Properties DataBase (PPDB)