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.
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.
Synthesis
The first synthesis of boscalid was disclosed in patents filed by BASF in 1995.
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.
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]
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.
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.[
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 in 2016.][
]
Human safety
Boscalid has low acute toxicity:[ the Codex Alimentarius database maintained by the FAO lists the maximum residue limits for it in various food products.]
Environmental effects
The compound is very persistent in field conditions[ and its environmental fate and consequent ecotoxicology have been reviewed.][
]
Resistance management
Fungal populations have the ability to develop resistance to SDHI inhibitors.
Brands
Boscalid is the ISO trivial name for the active ingredient which is formulated into the branded product sold to end-users. It was also known as nicobifen.[ but the compound has subsequently been sold under a range of product names.][
]
External links
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PPDB pesticides properties database entry for boscalid
