Description
A pyrimidine fungicide active against powdery mildew. It has a moderate aqueous solubility and a low volatility. Depending on local conditions, bupirimate may be moderately persistent in both soil and aquatic systems. It is moderately toxic to most fauna and flora species. It has a low oral toxicity to mammals and is a skin and eye irritant.
Uses
Bupirimate is a pyrimidine based fungicide with protective and curative activity for the control of fungal diseases by interfearing with nucleic acid synthesis.
Uses
Bupirimate is a systemic fungicide that provides protective and
curative control of powdery mildew (Podosphaera leucotricha) mainly in
pome fruits, stone fruits and glasshouse roses. Other uses include berries,
vines and cucurbits.
Definition
ChEBI: A member of the class of aminopyrimidines that is 2-ethylaminopyrimidine carrying methyl, butyl and dimethylaminosulfooxy substituents at posiitons 4, 5 and 6 respectively.
Production Methods
The commercial synthesis of bupirimate, a pyrimidine-based fungicide, typically begins with the reaction of ethirimol and N,N-dimethylsulfonyl chloride in the presence of potassium carbonate, ethyl acetate, and a catalytic amount of 18-crown-6 ether. This mixture is heated and refluxed to facilitate sulfonation. Once the reaction reaches partial completion, hexamethylenetetramine is added to adjust the pH to around 10, promoting further conversion. After several hours of continued reaction, the mixture is cooled, washed to neutralize, and the organic phase is separated. The solvent is removed, and the product is precipitated at low temperature, dried, and purified to yield bupirimate.
Mechanism of action
Systemic with curative and protectant action. Nucleic acid synthesis - adenosin-deaminase.
Metabolic pathway
Bupirimate degrades rapidly when exposed to sunlight. Minimal penetration
of bupirimate residues in treated apples was observed. Degradation
of bupirimate in/on fruit surfaces was mainly due to photolytic processes.
Metabolism in plants and animals is similar and includes the initial
cleavage of the dimethylsulfamate-pyrimidine linkage to yield ethirimol
which is also an active fungicide. Numerous degradation products were
generated from N-dealkylation, hydroxylation and conjugation reactions
and the opening of the pyrimidine ring (Scheme 1).
Degradation
Bupirimate (1) is stable in dilute alkaline solution, but readily hydrolysed
in dilute acidic solution. Bupirimate was rapidly decomposed in aqueous
solution when exposed to sunlight (Hassall, 1982). Cleavage of the
dimethylsulfamate-pyrimidine linkage yielded ethirimol [5-butyl-2-
ethylamino-6-methylpyrimidin-4-ol (2)] as the major product. Ethirimol,
an active fungicide, was degraded slowly under these test conditions.
Four additional minor products were also detected. Three of these
products were identified aS isomers of bupirimate, resulting from the
migration of the dimethylsulfamate moiety to the various nitrogen
molecules (compounds 3, 4 and 5; Cavell and Lincoln, 1974; Teal and
Skidmore, 1976).
