Beflubutamid-M

Beflubutamid-M is an enantiomerically pure molecule used as a selective herbicide in agriculture, primarily for controlling broadleaf weeds in crops such as cereals. It is the (S)-enantiomer form of the herbicide beflubutamid, which is more active than the original racemic mixture, allowing for greater efficacy at potentially lower doses and less environmental impact.

Common name (ISO): Beflubutamid-M

Synonyms: F4050 (development code)

Gross formula: C18H17F4NO2

Number CAS: 113614-09-8

Chemical class: Beflubutamid-M belongs to the chemical class of butanamide phenoxides (or phenoxy amidases), subclassified as a phenyl ether herbicide. In the context of herbicide classification, it is a carotenoid biosynthesis inhibitor (group F1 according to the HRAC). It acts specifically as a phytoene desaturase (PDS) inhibitor. It is a monocarboxylic amide compound, an aromatic ether, with fluorinated elements, which contributes to its selectivity and stability.

Development history: Beflubutamid-M is derived from the herbicide beflubutamid (racemic mixture), originally developed by UBE Industries (Japan) in the 1980s, with an initial patent in 1990. The racemic compound was commercially introduced in Europe in 2007–2008 (EU approved in December 2007) and used in formulations such as HerbaFlex for dicotyledonous weed control in cereals. The underlying chemistry (PDS inhibitors) has been known for about 20–30 years, but the pure (S) enantiomer was isolated and developed by Cheminova (acquired by FMC) starting in 2012, with a focus on increased herbicidal potency and residue reduction. Enantiomeric separation studies (using chiral HPLC) were published in 2012, and the official announcement occurred in 2018 as a "new molecule from old chemistry," targeting high-value crops such as wheat. There are no reports of resistance in weed populations to date, due to their specific mode of action.

Mode of action: Beflubutamid-M is a contact and translocated herbicide (moves via the xylem in plants), acting as an inhibitor of carotenoid biosynthesis. Specifically, it blocks the enzyme phytoene desaturase (PDS), essential for the formation of carotenoids that protect chlorophyll from photodegradation. This results in bleaching (chlorosis) of new leaves, necrosis, and death of sensitive weeds within 7–14 days after application. It is selective for cultivated grasses, as monocotyledons (such as cereals) metabolize the compound more rapidly. The (S) form is up to 10 times more active than the racemic form, allowing for lower doses (typically 50–100 g/ha).

Patent numbers: US 4,929,273 (Ube Industries, Ltd., 1990); WO 2018/119338 A1 (FMC Corporation, 2017); WO 2021/161100 A1 (Cheminova A/S, 2021); WO 2021/161101 A1 (Cheminova A/S, 2021); US 20200093136 (FMC Corporation, 2020)