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Names | |
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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 |
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ChemSpider | |
DrugBank | |
ECHA InfoCard | 100.115.343 |
EC Number |
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KEGG | |
PubChem CID | |
UNII | |
CompTox Dashboard (EPA) | |
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Properties [1] | |
C18H12Cl2N2O | |
Molar mass | 343.21 |
Appearance | off-white crystalline powder |
Density | 1.381 g/cm3 |
Melting point | 143 °C (289 °F; 416 K) |
4.6 mg/L (20 °C) | |
log P | 2.96 |
Hazards | |
GHS labelling: [2] | |
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H411 | |
P273, P391, P501 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
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]
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]
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 with 2-chloro-1-nitrobenzene and 4-chloro-phenylboronic acid, followed by hydrogenation of the nitro group. As the final product has been manufactured at the multi-tonne scale, considerable efforts have been made to improve yields. [8] [9]
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]
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]
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]
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]
The compound is very persistent in field conditions [1] and its environmental fate and consequent ecotoxicology have been reviewed. [4]
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]
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]