Boscalid

Boscalid is a broad spectrum fungicide used in agriculture to protect crops from fungal diseases. It was first marketed by BASF in 2002 using their brand name Endura.[3] The compound is an biphenyl amide derived inhibitor of succinate dehydrogenase.[4]

Boscalid
Names
Preferred IUPAC name
2-chloro-N-(4'-chloro[1,1'-biphenyl]-2-yl)pyridine-3-carboxamide
Other names
BAS 510F, Nicobifen
Identifiers
3D model (JSmol)
10092464
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.115.343
EC Number
  • 606-143-0
KEGG
UNII
  • InChI=1S/C18H12Cl2N2O/c19-13-9-7-12(8-10-13)14-4-1-2-6-16(14)22-18(23)15-5-3-11-21-17(15)20/h1-11H,(H,22,23)/f/h22H checkY
    Key: WYEMLYFITZORAB-UHFFFAOYSA-N checkY
  • C1=CC=C(C(=C1)C2=CC=C(C=C2)Cl)NC(=O)C3=C(N=CC=C3)Cl
Properties[1]
C18H12Cl2N2O
Molar mass 343.21
Appearance White to beige coloured crystalline powder
Density 1.381 g/cm3
Melting point 143°C
4.6 mg/L (20 °C)
log P 2.96
Hazards
GHS labelling:[2]
GHS09: Environmental hazard
H411
P273, P391, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

History

Inhibition of succinate dehydrogenase, the complex II in the mitochondrial respiration chain, has been known as a fungicidal mechanism of action since the first examples were marketed in the 1960s. The first compound in this class was carboxin, which had a narrow spectrum of useful biological activity, mainly on basidiomycetes and was used as a seed treatment. Many companies made analogues with the aim of expanding the range of species controlled and boscalid was successful in doing so.[5][6]

Synthesis

The first synthesis of boscalid was disclosed in patents filed by BASF in 1995.[7][8][9]

The aminobiphenyl required for reaction with the acid chloride of 2-chloronicotinic acid is prepared in two steps. The first is a palladium-catalysed Suzuki reaction, followed by reduction. As the final product has been manufactured at the multi-tonne scale, considerable efforts have been made to optimise these reactions.[8][9]

Mechanism of action

Succinate dehydrogenase inhibitors (SDHI) of this type act by binding at the quinone reduction site of the enzyme complex, preventing ubiquinone from doing so. As a consequence, the tricarboxylic acid cycle and electron transport chain cannot function.[10][11]

Usage

Boscalid has fungicidal effects against a wide range of crop pests. These include Alternaria, grey mold (Botrytis cinerea), white mold (Sclerotinia sclerotiorum), and powdery mildew (Uncinula necator). As a result, it has use in crops including fruits, soybeans and vegetables.[3][5]

Boscalid usage in the US to 2019 (estimated)

The estimated annual use of boscalid in US agriculture is mapped by the US Geological Survey and shows that it is mainly applied to fruit crops, with a maximum use of over 600,000 pounds (270,000 kg) in 2016.[12] Global sales in 2014 were estimated at $390 million. The compound lacks full control of important cereal diseases, especially septoria leaf blotch Zymoseptoria tritici, which has limited its potential.[5]

Human safety

Boscalid has low acute toxicity:[1] the Codex Alimentarius database maintained by the FAO lists the maximum residue limits for it in various food products.[13]

Environmental effects

The compound is very persistent in field conditions[1] and its environmental fate and consequent ecotoxicology have been reviewed.[4]

Resistance management

Fungal populations have the ability to develop resistance to SDHI inhibitors.[14] This potential can be mitigated by careful management. Reports of individual pest species becoming resistant[1] are monitored by manufacturers, regulatory bodies such as the EPA and the Fungicides Resistance Action Committee (FRAC).[15] The risks of resistance developing can be reduced by using a mixture of two or more fungicides which each have activity on relevant pests but with unrelated mechanisms of action. FRAC assigns fungicides into classes so as to facilitate this.[16]

Brands

Boscalid is the ISO common name for the active ingredient which is formulated into the branded product sold to end-users. It was also known as nicobifen.[17] Endura and Emerald are the brand names first used by BASF's formulations[3] but the compound has subsequently been sold under a range of product names.[1]

References
  1. Pesticide Properties Database (2023-07-25). "Boscalid". University of Hertfordshire. Retrieved 2023-08-10.
  2. "GHS Classification". pubchem.ncbi.nlm.nih.gov. 2023-07-22. Retrieved 2023-07-27.
  3. "Endura fungicide" (PDF). EPA. 2002-11-08. Retrieved 2023-08-10.
  4. Yibing, He (2006). "Boscalid" (PDF). FAO. Retrieved 2023-08-10.
  5. Walter, Harald (2016). "Fungicidal Succinate-Dehydrogenase-Inhibiting Carboxamides". In Lamberth, Clemens; Dinges, Jürgen (eds.). Bioactive Carboxylic Compound Classes: Pharmaceuticals and Agrochemicals. Wiley. pp. 405–425. doi:10.1002/9783527693931.ch31. ISBN 9783527339471.
  6. "History of SDHI-fungicides". frac.info. Retrieved 2023-07-26.
  7. US patent 5589493, Eicken, K; Goetz, N & Harreus, A et al., "Anilide derivatives and their use for combating botrytis", published 1996-12-31, assigned to BASF SE
  8. Glasnov, Toma N.; Kappe, C. Oliver (2010). "Toward a Continuous-Flow Synthesis of Boscalid" (PDF). Advanced Synthesis & Catalysis. 352 (17): 3089–3097. doi:10.1002/adsc.201000646.
  9. Takale, Balaram S.; Thakore, Ruchita R.; Mallarapu, Rushil; Gallou, Fabrice; Lipshutz, Bruce H. (2020). "A Sustainable 1-Pot, 3-Step Synthesis of Boscalid Using Part per Million Level Pd Catalysis in Water". Organic Process Research & Development. 24: 101–105. doi:10.1021/acs.oprd.9b00455. S2CID 212964123.
  10. Oyedotun, Kayode S.; Lemire, Bernard D. (2004). "The Quaternary Structure of the Saccharomyces cerevisiae Succinate Dehydrogenase". Journal of Biological Chemistry. 279 (10): 9424–9431. doi:10.1074/jbc.M311876200. PMID 14672929.
  11. Avenot, Hervé F.; Michailides, Themis J. (2010). "Progress in understanding molecular mechanisms and evolution of resistance to succinate dehydrogenase inhibiting (SDHI) fungicides in phytopathogenic fungi". Crop Protection. 29 (7): 643–651. doi:10.1016/j.cropro.2010.02.019.
  12. US Geological Survey (2021-10-12). "Estimated Agricultural Use for boscalid, 2019". Retrieved 2023-08-10.
  13. FAO / WHO. "Boscalid".
  14. Cosseboom, Scott; Hu, Mengjun (2021). "Identification and Characterization of Fungicide Resistance in Botrytis Populations from Small Fruit Fields in the Mid-Atlantic United States". Plant Disease. 105 (9): 2366–2373. doi:10.1094/pdis-03-20-0487-re. PMID 33719541. S2CID 232231834.
  15. "Fungicides Resistance Action Committee website".
  16. "Search Fungicides to find FRAC Recommendations". Retrieved 2020-09-04.
  17. "Compendium of Pesticide Common Names: Boscalid". BCPC. Retrieved 2023-07-27.
  • PPDB pesticides properties database entry for boscalid
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