FENAMIDONE

Fenamidone (13; RPA 407213; (S)-5-methyl-2-methylthio- 5-phenyl-3-phenylamino-3,4-dihydroimidazol-4-one) is a complex III inhibitor that does not derive from the strobilurins but rather belongs to the imidazolinone chemical class. Fenamidone is a white woolly powder, with the following characteristics: mp = 137 C; water solubility = 7.8 mg/L; logP = 2.8, and vp = 3.4×107 Pa. It was first described by Mercer et al. (39) in 1998. Only the S-enantiomer shows antifungal activity, thus offering a reduction in application rates over the racemic mixture.

Pure product is white woolly powder, no typical odor. Relative density 1.288. vapor pressure 3.4×10-4mPa(25℃), distribution coefficient KowlgP=2.8(20℃), Henry's constant 0.5×10-5Pa -m3 /mol(20℃). Solubility in water 7.8 mg/L (20°C). Solubility in organic solvents (20℃,g/L): acetone 250, acetonitrile 86.1, dichloromethane 330, methanol 43, n-octanol 9.7.

Fungicide.

ChEBI: A member of the class of imidazolones that is 3,5-dihydroimidazol-4-one substituted at position 2 by a methylthiogroup, at position 3 by an anilino group and at position 5 by phenyl and methyl groups (the S-enantiomer). A fungicide effecti e against Oomycete diseases such as downy mildew and certain leaf spot diseases.

The commercial production of fenamidone involves a complex multi-step chemical synthesis. One key method includes the reaction of methyl (2S)-2-phenyl-2-(isothiocyanato)propionate with phenylhydrazine in anhydrous tetrahydrofuran under an inert argon atmosphere, followed by cooling and further processing to yield the active compound (+)-(4S)-4-methyl-2-methylthio-4-phenyl-1-phenylamino-2-imidazolin-5-one.

Moderately toxic by ingestion and skin contact. Low toxicity by inhalation.

Protective and curative action. Respiration inhibitor (QoL fungicide).

Fenamidone has an acute oral LD₅₀ > 5,000 and an acute dermal LD₅₀ > 2,000 mg/kg in rats. Fenamidone is not a skin or eye irritant, is negative in the Ames test, and is nonteratogenic. It shows low toxicity to birds in acute and dietary studies but has a 96-h fish LC50 of 0.74 mg/L.

Fungicide